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147 Cards in this Set

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The max amount of KE of the ejected electron
KEmax=hf-(work function)
Photoelectric Work function=The minimum amt of energy required to liberate an electron from the surface of a metal.
What would be the effect from increasing the intensity of the irradiating light (with wavelength<Threshold wavelength) on a given metal surface?
THE KINETIC ENERGY OF THE EJECTED ELECTRONS WILL BE THE SAME AS THAT OF PHOTOELECTRONS EJECTED BY LOWER INTENSITY LIGHT, BUT MORE ELECTRONS WILL BE EXPELLED: The intensity of the radiation depends on the # of photons indident on the metal not the energy of the individual photons. Therefore, since each electron can absorb only 1 photon at a time, increasing the intensity will not increase teh KE of the photoelectrons; it will increase the # of photoelectrons.
Why is the work function for sodium less than that for Lithium?
THE VALANCE ELECTRON OF SODIUM IS LESS TIGHTLY BOUND THAN THAT OF LITHIUM DUE TO INCREASED NUCLEAR SHIELDING IN THE Na+ ATOM.
An electron falls from the 4s subshell to the 3p subshell. What occurs?
AN EMISSION OF ENERGY AND THE APPEARANCE OF A BRIGHT BAND IN THE ATOMIC SPECTRUM: Since the 4s subshell is at a higher energy level than the 3p, the electron must emit a photon because it loses energy in falling from 4s to the 3p.
Mass defect
The difference between the actual mass of a nucleus and the sum of the masses of the protons and neutrons.
Hybridization of the central atom and the molecular geometry
sp=linear
sp^2=trigonal planar
sp^3=tetrahedral
sp^3d=trigonal bipyramid
paramagnetic
An atom/ion is paramagnetic if at least 1 electgron is unpaired. Thus, an atom with an odd # of electrons must always be paramagnetic.
Half Lives
Longer half life means that it will dcay more slowly. Therefore, its rate constant will be less. By definition, k is inversely proportional to t1/2, so if t1/2 is larger by a factor of 2 then the corresponding k is smaller by a factor of 2.
Exoergic
A nuclear reaction that releases energy is called exoergic (just as a chemical reaction that releases heat is called exothermic).
The 2nd ionization energy for Na compared to Mg is?
GREATER THAN THAT OF Mg BECAUSE THE VALENCE ELECTRONS OF Na+ IS IN A 2p ORBITAL WHEREAS THAT OF Mg+ IS IN A 3s ORBITAL: Na+ has noble gas configuration therefore requires more energy to remove the electron.
When measuring the mass of all particles involved in the fusion of 2 nuclei, 2.2*10^31 kg of mass is unaccounted for. Approx how much energy must have been released?
E=mc^2.
E=(2.2*10^-31)(3*10^8)^2
E=(2.2*9)*10^(-31+16)
E=(19.8)*10^-15
E=2*10^-14
Compared to Propane, Nonane is?
More likely to be liquid at room temperature because of its longer carbon chain. Larger hydrocarbon molecules have higher boiling points. Therefore, nonane whould have a higher boiling point than propane and be more likely to be a liquid at room temperature.
1atm=760torr=760 mmHg
1atm=760torr=760 mmHg
Relationship between dipole moment and boiling point?
Increasing dipole moment is associated with increasing boiling point.
The central oxygen in dimethyl ether (CH3OCH3) most likely demonstrates?
COVALENT BONDING BETWEEN 2 of its sp3 orbitals and 2 sp3 carbon electrons. The oxygen and both carbons in dimethyl ether have 4 groups of electrons. Therefore, all of these atoms have sp3 hybridization.
Propane gas collected over water at room temperature does not exert fully 100% of the gas pressure in the collecting tube, because part of the contribution to gas pressure in the tube:
Derives from the vapor pressure of water. In addition to the propane gas in the region above the liquid water surface, there is also water vapor since water evaporates from the liquid surface due to its vapor pressure. Therefore, both the propane and the water vapor contribute to the total pressure of the gases.
Sodium metal will NOT explode when mized with:
a)water
b)bromine liquid
c)oxygen gas
d)neon gas
NEON
Sodium metal is a strong reducing agent. It will only react, and explode, in the presence of an oxidizing agent. The passage tells us that an oxidizing agent is a molecule that has 2 or more higly electronegative atoms covalently bonded together.
a)water: Although water is a very weak oxidizing agent, sodium metal explodes on contact with water.
b)bromine liquid: YES b/c Strong oxidizing agent
c)oxygen gas: YES b/c Strong oxidizing agent
d)neon gas: NO because its a noble gas and is inert to all chemical reactions.
What fuel mixure would you expect ot liberate more energy than H2/O2?
H2 and F2:
The energy liberated by a redox reaction depends directly upon the strengths of the oxidant and the reductant. So a reaction ihich is more exothermic than H2/O2 must involve a better reducing agent, a better oxidizing agen, or both. F2 is one of the most powerful oxidants commercially available because fluorine has the highest electronegativity of all elements.
If the ground state (n=1) energy for a H atom is -13.6 eV, the 1st excited state (n=2) is -3.4 eV and the 2nd excited state (n=3) is -1.5 eV, what photon energies would be emitted from 1 mole of excited (n=3) H atoms?
The energy of the photon released from an excited atom always = the difference b/w the excited energy level and the lower energy level. There are 3 possible drops an electron originally in level n=3 can make.
n=3 to n=1:
E=-1.5-(-13.6)=12.1 eV
n=2 to n=1:
E=-3.4-(-13.6)=10.2 eV
n=3 to n=2:
E=-1.5-(-3.4)=1.9 eV
Greatest # of electrons that exists in that energy level.
2n^2 rule
Ionizing forms of energy such as x-rays and nuclear radiation cause cellular dysfunction at the location of absorbance. Extreme exposure to x-rays might result in a framatic increase in the risk of developing:
BONE MARROW CANCER.
Chronic radiation exposure significantly increases the risk of cnacers of the tisuue where the maximum amount of radiation is absorbed. For instance:
1) Exposure to radioactive iodine (formed as nuclear waste) increases the risk of thyroid cancer becaue the thyroid concentrates iodine.
2) Exposure to radioactive gases (such as radon) cause concers of the throat and lungs, Ingested radioactive heavy metals(such as strontium and plutonium) concentrate in the bone matrix leading to increases in the occuraence of bone marrow and mylogenous leukemia (cancer of white blood cells produced in the bone marrow)
3) X-rays are absorbed by bone, increasing the risk of developing bone marrow and myelogenous leukemia.
Some toothpastes include strontium nitrate as an active ingredient because strontium ions can competitively bind to enzymes crucial for transmittance of sensory nerve impulses. These toothpastes therefore reduce the pain associated with sensitive gums. The ion that strontium is mimicking in the enzymatic cleft is?
Ca2+:
Enzymatic active sites are uniquely constructed to complement the shape and charge of their substrates. Therefore, Sr must be acting as a competitive inhibitor for a substrate with similar size and charge. Based upon size considerations, chemical compatability, and the ions that are important for nerve potentials, the best answer is Ca2_. Ca and Sr are in the same periodic family.
Why is there a drastic change in the nature of the electron affinity of O- as opposed to that of atomic oxygen?
Electrostatic repulsion makes it difficult to combine 2 particles with the same charge.
Why is the ionization energy of Fluorine greater than that of lithium?
THE VALENCE ELECTRONS OF LITHIUM ARE FARTHER FROM THE NUCLEUS THAN ARE THE VALENCE ELECTRONS OF FLUORINE.
Lithium atom is larger than fluorine atom. Therefore, the valence electrons of lithium atom are, on average, farther away from the nucleus than are the valence electrons of fluorine.
Wehn oxygen is binding to the iron atom in hemerythrin, it is acting as a?
(Cu-O-O-Cu)
LEWIS BASE:
In almost all cases, when a nonmetal atom forms a covalent bond with a metal ion (more appropriately called a coordinate covalent bond), the nonmetal is acting as a ligand and a lewis base by donating a pair of electrons to form the bond.
It was shown that chloroamine is a stronger ligand than ammonia. Why??
CHLORINE DONATES ELECTRON DENSITY TO THE NITROGEN ATOM, ENHANCING THE COORDINATE COVALENT BOND STRENGTH BETWEEN NITROGEN AND THE METAL ION.
The electronegativity of nitrogen is greater than that of chlorine. neutral halogens are very poor ligands. General rule is that the best ligands are those of nigtrogen and carbon which have a excess of electron density. The fact that chloroamine is a better ligand than ammonia tells us that the nitrogen atom in chloroamine must have more electron density than in ammonia.
Ammonium chloride is also formed when bleach and ammonia are mixed together. What is the phase of pre ammonium chloride at room temperature?
SOLID:
Ammonium chloride, NH4Cl is ionic and at room temperature, all ionic compounds are solids.
Electrolytes?
An electrolyte is a compound that dissociates and yields ions in solution.
Ex: Hydrogen chloride.
Ionic compounds only exist between atoms of very different electronegativities. With the exception of ammonium salts and a handful of strong acids, compounds consisting of all nonmetal elements are covalent compounds and weak electrolytes.
FYI: Hydrazine and Chloroamine is NOT an electrotye. They both are covalent compounds and poor electrolytes.
Free Radicals
A Radical has an odd # of electrons. They are very reactive because they have an atom without an octet; this is why radicals remove electrons from other molecules. THey do not necessarily have to be highly charged, nor do they have to involve electronegative atoms. Furthermore, since radicals have an unpaired electron, they must always have a net magnetic spin equal to that electron (+/-1/2). They can be classified as strong OXIDANTS because they remove electrons from other atoms to complete their octets. Therefore, the radicals are acting as oxidants/oxidizing agents. Radicals can be stabilized by resonance.
Ex: BrO3 has 7+3(6)=25 electrons
Based solely upon their relative intermolecular attractions, which one of the following ionic solids might have the highest melting point?
BaO because Ionic solids with the highest melting point will be the one with the strongest ionic interactions. The strength of ionic interactions is proportional to the charge of the ions. So the trick here is to find the ionic pair with the most highly-charged ions. (BaO: Ba is 2+ and O is 2-)
What are the characteristics of heating borosilicate glass?
1) The density of the glass decreases: Nearly all substances expand and become less dense when heated. This is due t the increased motion of molecules which, in turn, increases the spaces between the m0olecules.
2) The average molecular mass of the glass does NOT decrease
3) The amount of intermolecular spacing in the glass increases
4) The concentration of dissolved impurities remain the same: Since no chemial reactions or separation occurs during normal heating, the concentration of impurities must remain the same.
Degenerate means?
TO HAVE EQUAL POTENTIAL ENERGY
The formation of a coordinatio complexx makes the dz2 and dx2-y2 orbitals of the metal:
LESS STABLE: having lots of energy means having little stablity and vice vera. Since the crystal field increases the energy of the dz2 and dx2-y2 orbitals, it decreases their stability.
The fluoride ion is a stronger crystal field ligand than the iodide ion because the fluoride ion:
HAS A GREATER CHARGE DENSITY: Just as the mass density of a substance is its mass per unit volume, the charge density of a molecule is its charge pre unit volume. Both ions have a -1 charge yet the fluoride ion is smaller and has less volume than the iodide ion. Therefore, the charge per unit volume of the fluoride ion is greater than that of the iodide ion. keep in mind that the basicity increases as one moves up and to the left in the periodic table, so fluoride is a stronger base than iodide is.
A blue transition metal complex has a delta0 that corresponds to?
ORANGE PHOTONS: If a non-emitting object has a color blue, it must be absorbing blue's opposite color: orange.
Sodium-Vapor street lights are bright yellow. This means that the majority of photons being emitted by the lamps are?
YELLOW: light may appear yellow if its emitting more yellow photons than violet phrotons while emitting equal amounts(if any)of all the other wavelengths of visible light. The question implies that one color is emitted more than all the others. It has to be yellow, in the case of a yellow lamp.
If the Ksp of AgCl is 1.8*10^-10, and the Ksp of AgI is 9.1*10^-16, which of the following statements is true?
AgCl is more soluble than AgI. The solubility equilibrium constant, Ksp, is directly related to solubility. Since ksp for AgCl is greater than for AgI, AgCl must be more soluble.
In order to maintain a buffer solution of pH 7.4 at 25 degrees C, which of the following acids would be most appropriate?
H2Po4- (aq) with pKa=7.31. In general, it is best to choose a buffereing system for which the pKa of the conjugate acid is as close as possible to the desired pH. if the desired pH is 7.4, then, among the given choises the best conjugate acid to use is monobasic phosphate ion, H2PO4-.
A solution of AgCl (s) is at equilibrium at 25 deg C. If NaCl (s) is then added, which of the following will initially occur in the solution?
More AgCl(s) will form.
The only way to change the value of an equilrium constant is to change the temperature. Given the equilbrium reaction of AgCl, increaseing the concentration of Cl- (aq) by adding NaCl will shift the reaction ot the left, resulting in the formation of more AgCl(s). This is called the common ion effect.
All of the following properties of solutions depend on the # and not the kind of solute particles present.
The four Colligative properties are:
1) Boiling point elevation
2) Freezing point depression
3) Osmotic pressure depression
4) Vapor pressure depression.
FYI: Density is NOT a colligative property; its value depends on the identity of the substance.
HCl and NaCl both produce a greater boiling point elevation than deos acetic acid because?
Unlike acetic acid, HCl and NaCl both dissociate completely in water: HCl is a strong acid and NaCl is a soluble salt, these compouds will dissociate completely in water. Acetic acid is a weak acid, and weak acids do not completely dissociate in water.
As the molality of an electrolyte increases, why does iobserved (# of moles of ions produced when a mole of electrolyte dissociates) decrease?
MORE FREE IONS BEGIN TO PAIR UP. The ionizability constant, i, for a compound is the # of free particles produced when that compound dissolves in a particular solvent. If i were to decrease with the addition of a compound, this would imply that each molecule is yielding fewer free particles at higher concentrations. One exxplanation is that ions begin to pair up at the higher concentrations, so that 2 particles actually begin to behave like just 1.
Water boils at a lower temperature at higher altitudes. The most likely explanation for this is that at high altitudes:
THE ATMOSPHERIC PRESSURE IS LOWER THAN AT LOW ALTITUDES. Neither bond energy nor vapor pressure changes with a change in pressure. Boiling occurs when the vapor pressure of a liquid equals the atomspheric pressure. Water boils at a lower temperature at high altitudes because the atmospheric pressure decreases as altitudes increases.
As the temperature at which a reaction takes place is increased:
THE REACTION RATE AND THE RATE CONSTANT WILL INCREASE.
An increase in the rate constant always corresponds to a faster reaction rate. Increasing the temperature of a reaction always increases the reaction rate.
Addition of sodium acetate to a solution of acetic acid will cause the pH to?
INCREASE DUE TO THE COMMON ION EFFECT.
Sodium acetate is a basic compound, because acetate is the conjugate base of acetic acid, a weak acid ("the conjugate base of weak acid acts as a base in water"). the addition of a base to any solution, whether it is buffered or not, will increase the pH.
Given that the normal pH of human bodily fluids is 7.4, which of the following conjugate acid-base pairs would make the most effective buffer system under pysiological conditions?
H2PO4^-/HPO4^2- (pKa7.21):
The most appropriate buffer sustem is the one in which the pKa of the conjugate acid most closely matches the desired solution pH. If the desired solution pH is 7.4, then, according to the data in Table 1, this buffer system would be the most effective.
Among the following, which would most likely create a buffer solution when added in = amount to an aqueous solution of hydogen fluoride (HF)?
A)KF
B)HCl
C)NaOH
D)F2(g)
KF:
A buffer is a mixture of a weak acid, like HF, and its conjugate base. the conjugate base of HF is F-, which would be produced when KF is dissolved in solution.
Antifreeze is separated from water and replaced with an = mass of Substance X. If Substance X is soluble and has a lower molecular weight than the antifreeze, then:
THE RESULTING SOLUTION WILL SHOW INCREASED FREEZING POINT DEPRESSION.
Since Substance S has a lower molecular weight than the antifreeze, the volume of S to be dissolved in the water will be greater than the volume of antifreeze. More dissolved particles in the water implies a greater molality and, therefore, a greater freezing point depression.
When the unknown conjugate base derived from the unknown hydrogen halide HX is excited, its absorption spectrum would most likely show?
DARK BANDS:
Excitation of electrons in any atom requires the absorption of light. Dark bands are associated with absorption spectra and bight bands with emission spectra.
What is the explanation for the observation that CO2 and H2S are more soluble than N2?
1) CO2 and H2S produce ions in solution (they produce Hydrogen ions), while N2 does not.
2) CO2 and N2S are weak acids in water, N2 is not
3) The covalent bonds in CO2 and H2S are highly polar, but those in N2 are not.
4) NOT TRUE: CO2 and H2S are polar molecules, while N2 is not. FALSE because CO2 is a linear symmetric molecule. So while each C-O bond is polar, overall the CO2 molecule is nonpolar.
STP
0 degrees C and 760 Torr
Equilibrium and solubility constants depends on?
Equilibrium and solubility constants ONLY DEPENDS ON/FUNCTION OF TEMPERATURE, NOT PRESSURE, CONCENTRATION, OR THE PRESENCE OF A CATALYST. Those only shift the equilibrium sothat the original value of K is re-established.
Whats the relationship between rate constant and equilibrium constant of a reaction?
NO FORMAL RELATIONSHIP: While we often believe that there is a direct relationship between the rate (kinetics of a chemical realction and its equilibrium constant or delta H (thermodynamics), there is no formal relationshop between the 2. THerefore, there is no way of determining how long it will take a system out of equilibrium to reach equilibrium based solely on the value of K.
In the more complex haber-Bosch process, the in situ production of trace amounts of carbon monoxide slowly poins (binds to0 the metal catalyst. Why does this occur?
CO is a strong ligand:
CO is a ligand that forms strong coordinate covalent bonds. A ligand is a Lewis Base. While CO is toxic to most organisms because it is a strong ligand, the toxicity of a molecule to organisms does not mean that the molecule is industrially useless.
Activity coefficients
An activity coefficient is a function of temperature, pressure, and concentration. Over most concentrations, the activity oeffficient varies inversely with the concentration of the solution, with typical values being less than one.
In very dilute solution, the values of all activity coefficients approach?
1: The activity coefficient is a correction factor that accounts for the anomalous behavior of concentrated solution. In dilute solutions, the correction factor drops out; the activity coefficients equal 1.
Calcite will be least soluble in a solution of?
.1M CaCl2: The solubility of an insoluble salt will be lower in colutions if ions prsent in the salt are already in solution; this is the common ion effect. Therefore, Cacium carbonate will be less soluble in solutions that already contain calcium or carbonate ions in solution.
Calcite is more soluble in a solution of MgCl2 than in a solution of NaCl because of a greater degree of clustering. The ion-ion interaction that is primarily responsible for this is?
Mg2+----CO3(2-): The passage tells us that clustering is caused by the persistence of ion-ion interactiions after the salt lattice has broken up. The strength of ionic interactions is proportional to the charges of the ionic species. This is an attractive interaction, the ionic attraction between the magnesium and carbonate ion is stronger than that between sodium and carbonate because magnesium has a greater charge than sodium.
Which of the following ionic solutions should behave the most ideally?
.01M CsCl:
Ionic clustering is the principal cause of the departure of concentrated solution from ideality. The amount of ionic interaction in solution is proportional to the charge of the ions. Therefore, the ions that will experience minimal clustering, and thus, behave the most ideally, are ions with the least charge.
One gram of a salt was added to 200mL if oyre water and completely dissolved. That salt could have been?
A) AgCl
B)PbSO4
C)Cd(NO3)2
D)BaCO3
Cd(NO3)2:Very Soluable.
The Chernobyl catastrophe released tons of radioactive 131I into the environment. What treatment could minimize the ingestion of 131I on contaminated food?
HAVE VICTIMS INGEST SOLUTIONS CONTAINING NORMAL 127I.
We want to prevent 131I from entering the body. The radioactive decay rate of a nucleus is NOT a function of pressure, temperature, or concentration. The only thing one can do is to have people continuously exposed to 131I consume vasts amounts of normal iodine in hopes of shifing the equilibrium to the left.
131I(environment)<-->131I(thyroid)
Why would Cs+ concentrate in vesicles rich in K+?
Cesium salts are all very soluble (much more soluble than even sodium or potassium salts) and will not precipitate out of human electrolytic fluids. Furthermore, the chemistry of cesium is much more similar to other Group I ions such as Na+ and K+ than to Group II ions like Mg2+.
Kidney stones form over time as insoluble ionic compounds graducally precipitate out of solution. It has been found that these stones do not form in patients with more acidic urine. Which of the following salts might be expected to compose a substantial mass of the kidney stone?
A)NH4Cl
B)Na2CO3
C)CaCO3
D)Sr(NO3)2
The solubility rules tells us that A)NH4Cl, B)Na2CO3, and D)Sr(NO3)2 are VERY SOLUBLE. Therefore, C)CaCO3, calcium carbonate, a salt whose solubility is very pH sensitive is the best answer.
One gram of insoluble Pb131I2, containing only radioactive 131I was added to 100mL of water. Then one gram of soluble NaI(with 127I) was added to the solution and completely dissolved. What happens?
THE [131I-]DISSOLVED IN SOLUTION WILL INCREASE AFTER THE ADDITION OF Na127i BECAUSE OF THE DYNAMIC EQUILIBRIUM IN SOLUTION.
PbI2<->Pb2+ + 2I2
you might have thought that less 131I would be dissolved in solution because of the common-ion effect, but NO. The common ion effect tells us that the total [I] will decrease when NaI is added to the solution. Yet before the NaI is added, the [131I] is only about .001M (Ksp of PbI2 is about 10^-9)- most of the 131I will be replaced in the PbI2(s) with the normal I and, in the end, a lot more 131I will be dissolved in the solution.
Chelators, also called ligands, are molecules which stick to metal ions through a strong dipole-ion attraction in which an electron lone pair of the chelator is partially donated to the metal. This lone pair forms a highly polar, colvalent bond called a coordinate covalent bond, between the metal ion and the ligand. what is true?
A LIGAND MUST BE A LEWIS BASE.
A ligand donates electron density to the metal ion; hence, the positive charge of a metal ion decreases during chelation. Ligands must have an atom with atleast one pair of nonbonding electrons, and there is no nonbonding electrons in methane. Atoms with higher electronegativities will be less inclined to donate electron density. Therefore, nitrogen, which has a lower electronetativity than fluorine, will make a better ligand (better means it will form a stronger coordinate colvalent bond). ligands must be able to donate a non-bonding pair of electrons (a Lewis base is a compound which can donate a non-bonding pair of electrons to another molecule). Therefore, a ligand must always be a Lewis base.
Assume that the cation in the crown ether is a potassium ion. What is the charge of the crown ether-K+ complex?
Crown ether molecules is neutral. Since the charge of the potassium ion is +1, then the total charge of the complex is simply 0+1=+1.
Although the shape (secondary and tertiary structure) of the Ca2+ pump protein is highly complex, it would be logical to assume that an amino acid residue present within the channel might be?
GLUTAMIC ACID:
R-(CH2)2-COO-
because the role of ion conducting channels is to conduct ions. Ions are extremely hydrophilic due to their strong eon-dipole interactions with water. Therefore, the residues which constitute the channel should also be hydrophilic. Moreover, any residues whith ionic character should attract cations, not repel them. And since carboylate ions has a negative charge, it is a good choice.
Oxidation state
The quickest way to determine the oxidation state of any atom is to count the # of bonds that atom has with a more electronegative atom, and then form this #, subtract the # of bonds the atom has with a less electronegative atom.
The rate constant of a reaction does NOT depend upon:
THE FREE ENERGY OF THE REACTION: The rate constant, k, is only a function of temperature, steric orientation, and activiation energy. The free energy of the reaction, delta G, is a thermodynamic quantity, not a kinetic one.

IT DOES DEPEND ON:
1)THE TEMPERATURE OF THE REACTION
2)THE MOLECULAR SHAPE OF THE REACTANTS
3)THE ACTIVATION ENERGY OF THE REACTANTS
The vapor pressure of the mercury within the manometer does NOT depend upon:
THE EXTERNAL PRESSURE: The vapor pressure of a liquid (or solid) depends upon the velocities of the molecules and the molecular accessibility to the surface. The vapor pressure of a substance is independent of the external pressure.

IT DOES DEPEND ON:
1)DISSOLVED IMPURITIES
2)TEMPERATURE
3)THE INERMOLECULAR FORCES BETWEEN MERCURY ATOMS
What test could be used to identify the presence of aqueous NH4+?
ADDING NaOH AND SMELLING FOR AMMONIA: All ammonium salts are soluable. While the ammonium ion has a very low vapor pressure, ammonia is a gas a room temperature. Ammonia is very soluble in water, but as most of us know, the vapor pressure of ammonia in aqueous slution is still strong enough to make your eyes tear. Therefore, the addition of a base to convert NH4+ to NH3 and then a squick sniff, could be a qualitative test for the ammonium ion.
In one step to identify the anions in solution, gas bubbles formed after the addition of conc. HCl. This gas evolution confirmed the presence of the?
Carbonate Ion: The only common ions that will produce bubbles of gas after the addition of acid are the bicarbonate and carbonate ions. The reaction for carbonate in acid is:
CO3(2-)(aq) + 2H+ ->
CO2(g) + H2O (l)
What is the concentration of a solution made with 150g of lead iodide and 100 mL of water?
<.1 M : Lead Iodide is a very insoluble salt. The term insoluble means that these salts make solutions that are less than .01 M. Therefore, regardless of how much lead iodide you put in water, the concentration of dissolved salt is going to be very low.
Equilibrium Constant
Equilibrium Constant for a reacion ONLY depends upon temperature of the reaction.
Equilibrium Expression
Water Appears in the equilibrium expression if it is NOT the solvent. Water is ONLY absent when it is the solvent, i.e. aqueous-phase equilibria.
Acids
Strong Acids: pKa<0
Weak Acids: pKa>0

Therefore since Phosphoric acid has a pKa=2.1 it is a weak acid.
Sulfuric acid has a pKa<0 so it is a Strong acid.
Perchloric, perbromic, and periodic acids are all potent oxyhalo-acids with the general empirical formula HXO4. What explains why perfluoric acid, HFO4 doesn't exist at all?
1)Unlike the other halogens, fluorine cannot exceed an octet of valence electrons.
2) Unlike the other halogens, fluorine has a greater electronegativity than oxygen.
-However, while all the other halide ions are pH neutral in solution, the fluoride ion is basic.
The pH of a 1.0 M solution of H2SO4 should be:
NEGATIVE:
pH equals the negative log of [H+]. Since the first proton of H2SO4 is a strong acid, we can assume that all H2SO4 is dissociated into H+ and HSO4-. Therefore, the pH due to this first proton only is :
pH=-log[H+]=-log(1)=0.
however, unlike all of the other strong acids-HCl,HBr, HI, HNO3, and HClO4- we must also consider the small contribution of the 2nd acidic proton produced by the dissociation of HSO4- to SO4(2-). While this proton is weak, meaning that about 1 out of 1,000 of them actually dissociate, they still make the solution slightly more acidic. Therfore, the actual pH of a 1.0M sulfuric acid solution is less than 0.
Heartburn is caused when gastric fluids (pH=1) leak above the cardiac sphincter into the lower esophagus. If a patient took an antacid that neutralizes 99.9% of the HCl, the pH of the resulting solution would be?
pH=4:
If 99.9% of gastric juice which has [H+}=10^-1 is neutralized by an antacid, then only .1%=10^-4 M remains. The pH of a solution with a [H+] of [10^-4]
The pH of a solution produced when 10mL of gastric juice and 10mL of pure water are combined is about?
pH=1:
The [H+] of gastric juice is 10^/1 M. Doubling the volume of a 10 mL solution by adding water will cute [H+] in half, to 0.05M. The pH of this solution is
pH=-log(.05)=log(20)=log(10)+log(2)=1.3 therefore close to pH=1.
Why does a solution of NaF have a higher pH than HF?
HF is the conjugate acid of F-, and F- is the conjugate base of HF. The conjugate of a weak acid, such as HF is a base. Therefore, a solution of NaF will have a higher pH than a solution of HF.
The Chernobyl catastrophe released tons of radioactive 131I into the environment. What treatment could minimize the ingestion of 131I on contaminated food?
HAVE VICTIMS INGEST SOLUTIONS CONTAINING NORMAL 127I.
We want to prevent 131I from entering the body. The radioactive decay rate of a nucleus is NOT a function of pressure, temperature, or concentration. The only thing one can do is to have people continuously exposed to 131I consume vasts amounts of normal iodine in hopes of shifing the equilibrium to the left.
131I(environment)<-->131I(thyroid)
Why would Cs+ concentrate in vesicles rich in K+?
Cesium salts are all very soluble (much more soluble than even sodium or potassium salts) and will not precipitate out of human electrolytic fluids. Furthermore, the chemistry of cesium is much more similar to other Group I ions such as Na+ and K+ than to Group II ions like Mg2+.
Kidney stones form over time as insoluble ionic compounds graducally precipitate out of solution. It has been found that these stones do not form in patients with more acidic urine. Which of the following salts might be expected to compose a substantial mass of the kidney stone?
A)NH4Cl
B)Na2CO3
C)CaCO3
D)Sr(NO3)2
The solubility rules tells us that A)NH4Cl, B)Na2CO3, and D)Sr(NO3)2 are VERY SOLUBLE. Therefore, C)CaCO3, calcium carbonate, a salt whose solubility is very pH sensitive is the best answer.
One gram of insoluble Pb131I2, containing only radioactive 131I was added to 100mL of water. Then one gram of soluble NaI(with 127I) was added to the solution and completely dissolved. What happens?
THE [131I-]DISSOLVED IN SOLUTION WILL INCREASE AFTER THE ADDITION OF Na127i BECAUSE OF THE DYNAMIC EQUILIBRIUM IN SOLUTION.
PbI2<->Pb2+ + 2I2
you might have thought that less 131I would be dissolved in solution because of the common-ion effect, but NO. The common ion effect tells us that the total [I] will decrease when NaI is added to the solution. Yet before the NaI is added, the [131I] is only about .001M (Ksp of PbI2 is about 10^-9)- most of the 131I will be replaced in the PbI2(s) with the normal I and, in the end, a lot more 131I will be dissolved in the solution.
Which of the following ions can buffer a solution against both acids and bases?
H2PO4(-):
An ion that can buffer against acids and bases must have the ability to accept and donate a proton. the only ion given that can behave as both an acid and a base is h2PO4-.
H2PO4(-) <----> H+ + HPO4(2-)
H2PO4(-) + H+ <---> H3PO4
Why is Mg(OH)2 (s) more soluble in pure water than blood (pH 7.4)?
Since the pH of blood is greater than 7, the concetnration of OH- is greater than that of H+. Due to the presence of more OH- in the blood than in pure water (pH=7), the common0ion effect tells us that the solubility of MG(OH)2 should be less in blood than in pure water.
Titrations
Teh titration of a strong acid with a strong base (or vice versa) has an equivalence point which occurs at pH 7.
What is the pKa for the conjugate acid of the solute in solution X?
The pKa of the conjugate acid of solute X can be determined from the titration cureve. 1st, the pKb for solute X is = to the pOH of the solution when it is 1/2 titrated: half the distance to the equivalence point on the x axis. At 25 degrees C, the pKb of solute X + pKa of solute X's conjugate acid =14. pH of initial solution is 10.7. Since the pH at the 1/2 equivalence point is between 7 and 10.7, the pOH at this point is between 14-10.7=3.3 and 17-7=7, therefore the pKb is between 3.3 and 7/ Since the pKb is less than 7, the pKa of its conjugate acid must be greater than 7.
Why is this statement False?
Given that the Ka of the acid H2X is 10^-10, then the Kb for H2X must be 10^-4 at 25 degrees C.
The sum of the pKa of an acid (H2X)+ the pKb of its conjugate base (HX-)=14 at 25 deg C. NOT the pKa + pKb of the same molecule.
Which one of the following solutions would hav ethe lowest freezing point temp?
1) .1M NH4HO3
2) .1M NaOH
3) .1M BaCl2
The solution with the greatest # of dissolved particles will have the lowest melting point. Since the concentrations of all the solutions are identical, we must consider the # of ions produced when each molecule dissolves. The dissolution of ammonium nitrate and sodium hydroxide produce 2 ions each, while the dissolution of barium chloride produces 3 ions.
Identify the buffering solution:
1) HCl and NaCl
2)H2SO3 and HSO3-
3)HF and CH3F
4)NaOH and Na2O
H2SO3 and HSO3-:
A buffer must consist of the conjugate pairs of a weak acid and base. Hydrochloric acid is a strong acid, and sodium hydroxide is a strong base. The conjugate base of HF is F-, not the covalent compound CH3F. Therefore is must be H2SO3 and HSO3- because weat base bisulfite ion, HSZO3- is the conjugate base of the weak acid sulfurous acid.
The pH of the solution that results after mixing 10mL of 1m0M HCl and 10mL of 1.0M NH3 is the same as the pH of?
A 0.5M solution of NH4Cl:
One HCl will react with one NH3, to give 1 NH4Cl. So in this reaction the # of ammonium chloride molecules will be the same as the original # of HCl and the original # of NH3. However, we are mixing 2 solutions with identical volumes, so in essence, we are doubling the volume of the solution. Thus if the # of NH4Cl is the same as the initial # of HCl, but the volume is doubled, the solution will be 1/2 as concentrated.
What is the isoelectric point for serine?
The isoelectric point, pI, or an amino acid with only 1 acid and base group iss just the average of the pKa's. The average of 2.2 and 9.2 is just 5.7.
amino acids
The passage states that at a pH one unit lower than the pKa, all the carboxylic acid groups are protonated. At a pH one unit highter than the pHa, all of the carboxylic acid groups are deprotonated. Thus, for asparginine, where the pKa is 2, at a pH=1 implies that all are protonated and at a pH=3, implies taht all are deprotonated. So at pH 2 (=pKa), half will be protonated and half will be deprotonated.
Why are disulfide bridges much more stable than those of peroxides (oxygen-oxygen single bonds) even though sulfur and oxygen have the same valence configuration?
THE ELECTRON CLOUDS OF SULFUR ATOMS ARE LARGER AND MAY OVERLAP TO A GREATER EXTENT.
Larger atoms may form stronger covalent bonds because of a larger area of electron overlap.
The vaporization of water requires more heat than does the melting of ice. Because?
MELTING REQUIRES THAT ONLY A FRACTION OF INTERMOLECULAR FORCES BE BROKEN WHILE VAPORIZATION REQUIRES COMPLETE SEPARATION OF MOLECULES.
The energy associated with phase changes is due to the formation or cleavage of intermolecular bonds. The energy required to vaporize a liquid is always greater than the energy to melt a solid, because all intermolecular bonds must be broken in order to form a gas.
A substance has a heat of formation of 0. This is best explained by?
THE SUBSTANCE IS AN ELEMENT IN ITS STANDARD STATE.
A substance is in the gas phase at STP. As the pressure of the surroundings is progressively decreased at constant temperature, the gas will eventually undergo:
NO PHASE CHANGE:
A gas can be liquefied by fringing the molecules closer together. This can be accomplished by either increasing the external pressure on the gas or by decreasing its temperature. Neither of these is done here, so this gas will remain a gas.
A reaction occurs that results in a set of products with more stable bonds and more orderly arrangement than were present in the reactants. Which of the following is true of this reaction?
THE ENTHALPY AND ENTROPY CHANGES ARE NEGATIVE:
In order for the products to be more stable, they must have lost energy; thus delta H is negative. If the product have a more orderly arrangement than the reactants, then the entropy decreased; thus delta S is also negative.
According to the Kinetic theory, what is true about ideal gases?
1) All collisions among gas molecules are perfectly elastic.
2) There are no attractive or repulsive forces between gas molecules.
3) For a sample of gas molecules, average kinetic energy is directly proportional to temperature
4) NOT TRUE: There is no transfer of kinetic energy during collisions between gas moelcules: Gas molecules ARE allowed to exchange kinetic energy with each other.
A sample of benzene undergoes a phase change from a gas to liquid. The enthalpy change associated with this process is:
NEGATIVE, beause bonds are FORMED IN THE PROCESS. The cleavage of bonds requires energy, while the formation of bonds releases energy. During condensation, intermolecular bonds are being formed to hold the molecules together into a cohesive liquid.
The molarity and the molality for a solution are never = when?
THE SOLUTE OCCUPIES A SIGNIFICANT VOLUME OF THE OVERAL SOLUTION.
When the solvent has a density of 1.0 kg perliter, such as water, the molarity and molality of solutions with solutes that take up no volume (such as ionic compounds) will be identical. Aqueous (water) solutions that have different molalities and molarities are most often solutions with soluble, organic liquids such as methanol or acetone.
If 10g of each of the gases He and Ne were heater to 1000 deg C, which 1 would provide more rocket lift?
He:
2 gases with different masses have the same KE at the same temperature, but not the same momentum. Momentum=mv. The taotal masses of both gases are the same (10g), so all we have to do is choose the gas with the greater velocity. Lighter gases at the same temperature have greater velocities, so the helium would provide more lift.
The space shuttle's main tant storing the liquid Hydrogen and Oxygen fuel has microsopic cracks and holes which allow a very small amount of the liquid to vporize and escape to the environment. What is true?
1) Hydrogen gas will escape about 4 times faster than Oxygen gas.
2) The regions of escape will be colder than the surrounding tank: Since vaporization is an endothermic process (it absorbs heat), as the liquid vaporizes, it will cool the surroundings.
3) The condensation of hydrogen and oxygen is an exothermic process: Condensation is an exothermic process (it releases heat).
Under what conditions does water vapor approach ideal behavior?
LOW PRESSURE, HIGH TEMPERATURE:
The major forces which cause gases to deviate from ideality are most influential when gas molecules are very close together and moving slowly.Therefore, gases are most ideal when their molecules are far apart and zipping around. These conditions corresponds to low pressure and high temperatures.
Which gas could have served as an inert gas in an experiment?
A) H2
B) N2
C) O2
D) F2
N2:
If a noble gas like helium or argon is not readily available, chemists often usse nitrogen as an inert gas. Oxygen and fluorine are strong oxidizing agents and are very reactive gases. Hydrogen is a mild reducing agent, and is used to reduce organix compounds. Nitrogen, makes up 80% of the Earth's atmosphere beause it has accumulated due to its lack of chemical activity. Furthermore, diatomic nitrogen has an internal triple bond that give N2 a very high bond dissociation energy, hence N2 is not very reactive.
One of the limitations of using a gas as a shock absorbing cushion is that under high pressures, the gas may liquefy and lose compressibility. Which of the following gases would be the best one to use in light of this concern?
A) Carbon Dioxide
B) Water Vapor
C) Bromine gas
D) Ammonia gas
CARBON DIOXIDE:
We want a gas with the lowest condesnsation/boiling point (BP). Both water and bromine are liquids at room temperature, so they are poor choices. Ammonia and carbon dioxide are gases, however, the boiling point of CO2 is much lower than that of ammonia. CO2 with its dispersion forces, will have a lower BP than ammonia, with its hydrogen bonds.
Osmosis
In osmosis, the direction of water flow is always intoo the solution of higher solute concentration:
All equilibria are dynamic equilibria. While volumes of the liquids on each side of the membrane are not changing, individual water molecules are still passing through the membrane from both directions, just in = numbers. The inetic energy of a molecule is proportional to its temperature and the = for osmotic pressure is a function of temperature. osmotic pressure opposes the direction of osmosis (water flow).
Osmotic pressure=
pi=i*deltaM*R*T
i=ionizability factor
deltaM= difference in the molarities of the solutions
R= gas constant (=.0821 L atm/mol*K)
T=Temperature in Kelvin
molarity/molality
1) The molarity of a solution may change with temperature and pressure
2) The molalality of a solution is independent of temperature and pressure.
Molality=moles of solute per kg of solvent.
Why does MgSO4 have a greater association in water than does NaCl?
The electrostatic attraction between the magnesium and sulfate ions is greater than between sodium and chloride ions:
Neutral magnesium and sodium atoms have about the same size because they're next to each othe ron the periodic table. However, the magnesium ion is substantially smaller than the sodium ion because it has a +2 charge as opposed to a +1 charge of sodium. Hydrogen bonds only occur between Hydorgens of N-H, H-F, O-H and another N, O, or F; Chlorine never participates in hydrogen bonding. Ions associate with one aother because opposite charges attract. If the magnesium and sulfate ions associate more than sodium and chloride, this implies that the Mg2+ and SO4- are feeling each other's charge more.
Under what condition should the ionizability factor of salt be equal to its van't Hoff factor?
LOW CONCENTRATIONS: Van't Hoff facts only begin to depart from the theoretical ionizability factor at higher concentrations. Therefore, one would expect that in very dilute solutions, the van't Hoff factor should = the ionizability factor.
A theoretical scientist computed the freezing point depression of a .01 m solution of potassium sulfate using the expected ionizability factor instead of the actual van't Hoff factor. Relative to the experimental result, his computed result would be?
10% too HIGH:
In nearly all instances, using the ideal ionizability factor overestimates the # of free ions in solution. Based upon the passage, the difference between the van't Hoff factor and expected i for potassium sulfate is about 10% since (3.00-2.70)-.3/2.7=.1 and therefore 10%.
Bhor atom
Bohr atom is any atom that has only 1 electron.
For example: Be3+
If a sample of air ("the system") absorbs more energy than it emits, then its q is:
POSITIVE:
By definition, when the net heat (energy) flux is into the system, q is positive. Remember that
deltaE=q+w so q=deltaE-w. So if the system is absorbing energy, deltaE is positive, thus q must be positive because no work is being done in this case.
Consider that the Earth is in radiative equilibrium, then the # of emitted IR/microwave photons should be?
GREATER THAN THE NUMBER OF ABSORBED VISIBLE PHOTONS:
Just as much energy is being absorbed by the Earth as is being radiated to space, and that each individual IR/microwave photon has less energy than each individual visible photon. Based upon this, more IR/microwave photons must be emitted by the Earth because each photon carries less energy than each visible photon. Note that while visible photons are only absorbed half of the day (during daylight hours), the Erth is constabtly emitting IR/microwaves in an attempt to cool off.
Some random true statements
1) Gases typically have more entropy than solids
2)Under standard conditions, pure elements in their natural phase have Hf^o and Gf^o of zero.
3) STP and standard conditions do not describe the same conditions.
A molecule that has 2 or more highly electrovegative atoms covalently bonded to one another will always be an OXIDIZING agent. Is H2O2 or SO2 a better oxidizing agent? Why?
Oxidizing agents can be recognized because they have 2 or more highly ectronegative atoms directly bonded together. Considering that S is not a highly electronegative atom and that the structure for SO2 has both O's doubly bonded to the S, sulfur dioxide is not an oxidizing agent by this definition. Hydrogen peroxide is a powerful oxidizing agent because its structure is
H-O-O-H the 2 Oxygen atoms are directly bonded together.
If the cylinder has adiabatic walls, then the walls:
PERFORM THE SAME FUNCTION AS DO ISOTHERMAL WALLS:
Adiabatic walls are defined as barriers that do not permit the transfer of heat. Thus any heat produced by a system will remain in the system.
For example, the walls of a good coffee cup are insulators, that is, they prevent heat transfer with the environment. This is an adiabatic (or closed) system.
Anode
Cathode
*CATIONS FLOW TO THE COPPER CATHODE: Cu gets REDUCED!
*ANIONS FLOW TO THE ZINC ANODE: Zn gets OXIDIZED!
Oxidizing and Reducing agents
An oxidizing agent gets reduced, that is it gains electrons. And a Reducing agent gets oxidized, that is it looses electrons. The better one is one that occurs spontaneously.
*The oxidizing and reducing agents are ALWAYS REACTANTS, not products, in a redox reaction.
*Best one is the one with the highest reduction potential.(Greatest positive E^o)
Salt Bridge
SERVES AS A CONDUIT THROUGH WHICH IONS CAN FLOW FREELY. It is NOT the site of chemical reactios. It allows for the gradual migration of ions from one compartment (1/2 cell) to the other.
When an element is OXIDIZED it will:
LOSE ELECTRONS, AND ITS OXIDATION STATE WILL INCREASE:
Oxidation is defined as an increase in oxidation number and corresponds to the loss (or apparent loss) of electrons.
In an electrolytic cell containing molten MgCl2(l)?
Mg2+ is reduced at the cathode.
Cl- is oxidized at the anode.
*The anode is always the site of oxidation, and the cathode is always the site of reduction. Mg2+ will not lose any more electrons and Cl- will not gain any more elctrons.
If an extremely strong reducing agent is added to a aqueous solution of VO2+, the resulting species of vanadium will most likely be?
Vanadium (II), because it is the lowest oxidation state.
It takes a stronger reducing agent to bring about hte reduction to V(II) than to V(IV). Therefore, it seems likely that an extremely strong reducing agent would indeed produce V(II), which is the lowest oxidation state.
If 6 moles of permanganate anion are required to completely oxidze a sample of vanadium (II), how many moles of permanganate ion would be required to completely oxidize an equivalent molar sameple of vanadium (IV)?
Each vanadium atom must lose 3 electrons to go from vanadium (II) to vanadium (V), but only one electron to go from vanadium (IV) to vanadium (V). Therefore, the # of electrons that must be removed from vanadium (IV) is 1/3 the # that must be removed from vanadium (II) to achieve the fully-oxidized vanadium (V) state. So, if 6 moles of permanganate ion are required for the complete oxidation of vanadium (II), only 2 moles will be required for the complete oxidation of vanadium (IV).
Calculating Total Cell Voltage
REMEMBER: When calculating total cell voltage, the E^o values for the half-reactions are not multiplied by any stoichiometric factors that are used to balance the #s of electrons gained and lost in the overall redox reaction. Therefore, there is no need to balance 1/2 reactions.
Random Statements
1) The total output current over the entire lifetime of an electrochemical cell is only dependent upon the mass of the reacting electrodes, not on their shape: The total current output of a battery is dependent upon the # of moles of the reactants, nothing else.
2) Given that the highest oxidation potential normally observed is +3.03 volts (lithium) and the highest reductive potential is +2.87 (fluorine), then any battery which has an output voltage of more then any battery which has an output voltage of more than 5.90 volts must have several cells wired in series: Lithium-fluorine batteries are the highest voltage, single-cell battery possible, 5.9V.
3) The voltage of a cell is independent of the size or shape of the electrodes.
4)FALSE: Although there is no direct correlation between voltage and current, it is true that a redox reaction with a positive voltage will produce a positive current, and a redox reaction with a negative potential will produce a negative current: A cell with a positive voltage will produce a positive current, a cell with a negative voltage (non-spontaneous reaction ) is considered "dead" and will produce no current (Icell=0)
In the Nernst equation, what is the purpose of the factor 2.303?
It is a conversion factor between natural and base 10 logs. 2.403 is a conversion factor between natural (base e) and common (base 10) logs.
Standard Conditions
Standard Conditions:
Temperature: 25 degrees C=298K
Pressure: 1 atm, 760 Torr
Concetnration of all solutes is 1 molar.
The Statue of Liberty consists of a copper shell internally supported by an iron framework. Unti its renovation, the monument had sustained severe corrosion of the inner framework because the original isulating pads which prevented metal-metal contact at copper-iron interfaces had weathered away. Why is it important to prevent the copper and iron from making contact.
BECAUSE COPPER METAL IS SLOWLY OXIDIZED IN MOIST AIR, IRON SERVED AS A SACRIFICIAL ANODE:
In the absence of any other substances, a junction between 2 different metals poses no problems because metals can never act as oxidizing agents becoming anions. However, in the presence of oxidizing agents, such as oxygen, both metals will be attacked by O2. Yet, if the metals are in contact, the metal with the higher reduction potential (more corrosive resistant), in the case copper will replace electrons lost to oxygen by taking them from the metal with the lower reduction potential, in this case iron. So for the Statue of Liberty, over time, the corrosion of copper was inadvertently minimized at the expense of the iron which was being oxidized by both O2 and Cu2+. The iron framework served as a sacrificial anode.
Aluminum metal has a lower electronegativity than iron, yet reacts very slowly with oxygen in moist air because of a hard, protective alumunum oxide coat that protects all exposed surfaces. Unver which of the following conditions would aluminum be readily corroded?
IMMERSED IN A SOLUTION OF HCl:
All metal oxides are alkaline. Therefore, immersion in an acid bath will strip off these protective coats and allow the acid to begin to oxidize the metal below. For many metals, such as Al, Zn, and Mg, this reaction is rather fast, and copious amounts of H2(g) can be generated.
Electrolytic Cell
Galvanic Cell
Electrolytic Cell: ANODE IS THE POSITIVE ELECTRODE and CATHODE IS THE NEGATIVE ELECTRODE.
Galvanic Cell: ANODE IS THE NEGATIVE ELECTRODE and CATHODE IS THE POSITIVE ELECTRODE.
The electrolysis of water laced with some Na2SO4 produces 1 mole of pure hydrogen. What is true?
THE PRESENCE OF SODIUM SULFATE INCREASES THE CONDUCTIVITY OF THE SOLUTION.
Oxygen is being oxidized (-2 --> 0 in oxygen gas) during the electroysis of water. Water is a polar molecule with a net charge of 0. Therefore, in an applied electric field, the water molecules will point their + region at the - terminal and point their - region at the + terminal, but they will not move in either direction. Hydrogen is produced 2 as fast as oxygen because there are 2 hydrogen for every oxygen in a water molecule. Na2SO4 is a soluble salt, and is therefore a good electrolyte.
In the electrolysis of potassium fluoride, the best material to use to construct the electrode might be?
GRAPHITE:
The electrolysis of KF will produce potassium metal and fluorine gas. Fluorine gas is an extremely poten oxidizing agent. Therefore, it would be stupid to use it, metallic electrode which would make a good reducing agent. Even inert platium will be oxidized by fluorine gas. The best choice is to use a nonmetal, covalent conductor, such as graphite.
What is the oxidation state of the carbon atom in the cyanide ion?
Nitrogen bas a greater electronegativity than carbon, it will have its oxidation state of choice which is 03. The next step is to recall that the charge of an atom or molecule = the sum of all the oxidation #s in the atom or molecule. Since the cyanide molecule has a sharge of -1, the oxidation state of the carbon atom must be +2.
Chelation is an example of a:
LEWIS ACID-BASE REACTION:
Chelation is the process of forming coordinate covalent bond between e- pair fonor (ligand) and e- pair acceptor (metal ion). Therefore an acid/base reaction.
In the figure the arrow under the light bulb (arrow pointing from the (+) Copper electrode to the (-) Zinc electrode, indicates the direction of?
(Galvanic Cell)
OPPOSITE TO THE ELECTRON FLOW:
It is convention that the arrow showing the direction of the current represents the direction a positive particle would travel in the applied potential field. Since electrons are negatively charged, the actual electron flow is always opposite this current arrow. But without thjis inofrmation, you could still determin which way the electrons were flowing based upon the fact that free electrons are being produced at the zinc electrode
(Zn --> Zn2+ +2e-)
and then are cunsumed at the copper electrode
(Cu2+ + 2e- --> Cu)
So the electrons must be flowing from the zinc electrode to the copper electrode.
Note: atoms in a solid metal do not micrate.
Any cell having a positive voltage must be powered by a reaction that is?
(Galvanic cell)
SPONTANEOUS:
Since G^o= -nFE^o, when a cell has a positive voltage, the reaction must be spontaneous. Most often, spontaneous rections are exothermic, not endothermic.
FYI: A reaction that is at equilibrium has a 0.00 voltage.
What would happen if a student accidentally placed the zinc electrode directly into the copper solution?
(Galvanic Cell)
1) The light buld would go out: If a you allow the reductant and the oxidant to come in direct contact, thereby causing a short circuit, the current through the wire would stop because the electrons will take the short way to the oxidant which is right through the solution.
2)The zinc electrode would be immediately encrusted with a layer of copper metal: Copper ions that come in contact with the surface of the zinc electrode would be reduced to copper metal and deposited onto the zinc electrode.
3)The copper electrode would NOT be immediately encrusted with a layer of zinc metal: Zince ions cannnot spontaneously oxidize copper metal because this process has an E^ocell of -1.1V (its the reverse of the reaction in a galvanic cell).
4) The solution would warm up: Since the reaction is no longer producing an organized electrical flow, all of the energy of the reaction would be expelled as heat.
Which of the following will reduce the electrical current of a galvanic cell?
1) Let the solutions evaporate to dryness
2) Remove the salt bridge
3) Precipitate out the copper ions
*If the solution were allowed to solidify or precipitate out the copper ions, the reaction would completely stop. Copper ions require the ability to float to the cathode in order to be reduced. It is difficult to floate without any water. Removal of the salt bridge, would prevent migratory ions to compensate the charge flow of the electrons. THis means that after a second or so, the arriving electrons at the copper cathode would give it an excess negative charge. The anode would develop an excess positive charge because while it is exporting electrons to the cathode, the cations which are being formed are not allowed ot migrate to the cathode. Therefore, very quickly, electrons would be unable to flow from the attacking positive anode towards the repulsive cathode because of electrostatic force.
4) FALSE: Precipitate out the zinc ions
Electrons flow from the?
Anode to the cathode.
Reactions in HCl and H2SO4 produced an odorless, colorless gas, while those in HNO3 produced an acrid orange0brown gas. These gases were hydrogen and ?
NITROGEN DIOXIDE:
NO2 is an acrid, orange-brown gas.
It couldn't have been ammonia, sulfur dioxide, or nitrogen because they are all colorless gases and the ordorless, coloroless gas was hydrogen.
based upon this student's experiment, which other strong, oxidizing acid (like HNO3) would corrode all of the metals in this experiment?
HClO4:
This is a strong acid that has a conjugate base which is a powerful oxidizing agent in its own right. Remember that an oxidizing agent is a molecule which has 2 or more highly electronegative atoms bound together. Perchloric acid is a strong acid, and teh perchlorate ion, ClO4- is a powerful oxidizing agent.
Kinetic molecular theory
The Kinetic theory of gases attempts to explain the macroscopic properties of gases from a microscopic perspective. The basic assumptions are:
1) The gas particles are separated by distances much greater than their size. ( Negligible volume)
2) The only intermolecular forces occur during collisions, which are totally elastic. ( No repulsive forces)
3) The gas particles are moving in a random fashion with a distribution of speeds.
4) The AVERAGE kinetic energy of a gas is directly proportional to the absolute temperature. (collides without a net loss in kinetic energy).

Note: The AVERAGE Kinetic energy is constant at a particular temperature so is the AVERAGE speed. This does not imply that the speed of a particular molecule remains constant, it changes with each elastic collision. It is the average speed that remains constant. The sum of the kinetic energies of the colliding particles does not change.
Ideal gas vs. Real gas
Ideal gases obey the ideal gas law at all temperatures and pressure.
Real gases follow the ideal gas law only at high temperatures and low pressures. At low temps real gases exhibit a lower Volume than Charles's low would predict. This is b/c attractive forces exist between the molecules of a real gas. Whereas, it is assumed that the molecules of an ideal gas do not interact in any way. We know that these attractive forces exist b/c if we continue to lower the temperature of a gas, the molecules associate with each other, which eventually leads to condensation. Ideal gases neer condense; they just continue to follow Charles's law. Aother way in which real gases differ from ideal gases, is that at high pressures, real gases occupy a larger volume than predicted by Boyle's law. This is b/c the ideal gas law does not take into consideration that volume occupied by the molecules themselves. It is assumed that the volume predicted is the volume that the gas would occupy if the molecules theselves occupied no space.
Why are boiling points a better indication of intermolecular bonding than melting points?
Crystallization depends upon molecular symmetry as well as intermolecular bonding. Boiling point is strongly dependent upon intermolecular bond strength.