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144 Cards in this Set
- Front
- Back
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What is the mass number of an element |
Mass Number (A) = # of protons and neutrons |
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What is the figure for 1 amu? |
1.66x10^-24 grams |
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What is the difference between the atomic mass and the atomic weight of an atom? |
The atomic mass is the sum of the masses of all the protons and neutrons in an atom. Atomic weight is the mass (in grams) of one mole of an atom. For example, the atomic mass of Carbon-12 is 12 amu, while its atomic weight is 12 g/mol. In other words, one gram is equal to one mole of amu. |
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What is the atomic mass unit a measure of? |
It is the average mass of a proton and neutron. |
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What is the trend on the periodic table for increasing atomic radius? |
To the left and down (opposite of electronegativity) |
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What is conserved for all elements in the same period of the periodic table? |
Outermost electrons have the same principal quantum number (shell number). |
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What do all elements in the same group (column) have in common? |
They all have the same # valence electrons (and similar chemical properties, as a result). |
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What is Avagadro's #? |
6.022x10^23 |
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True/False: Electrons lose energy when when they jump from a lower quantum level to a higher level. |
False. They absorb energy when transitioning from a lower 'n' to a higher 'n'. |
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What does the Heisenberg uncertainty principle state? |
It is impossible to simultaneously determine the momentum and position of an electron. |
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What does the Pauli exclusion principle state? |
No two electrons in a given atom can possess the same set of four quantum numbers. |
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True/False: the energy difference between two shells decreases as the distance from the nucleus increases. |
True |
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What does the Magnetic Quantum Number (m sub l) represent? |
The particular orbital within a subshell where an electron is highly likely to be found at a given moment in time. |
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What does the Azimuthal Quantum Number (l) indicate? |
It indicates the number of subshells within "n". |
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What does Hund's rule state? |
The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins. |
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What is the maximum number of electrons allowed in a single atomic energy level in terms of the principal quantum number "n"? |
2n^2 |
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Describe the difference between paramagnetic and diamagnetic. |
Materials made of atoms with unpaired electrons are paramagnetic, because the magnetic field of unpaired electrons will align their spins with the magnetic field (hence the prefix para). Materials consisting of atoms without unpaired electrons will be slightly repelled by a magnetic field and are diamagnetic. |
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What is the formula for momentum? |
momentum (p) = mass (m) x velocity (v) |
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Fact |
Subshells prefer to be either empty, half-full, or completely full. For example, the 3d subshell doesn't like 7 or 8 electrons. It wants 5, 10, or 0. |
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What is the formula for calculating Dipole Moment? |
u = qr, where q = charge magnitude, and r = distance between two partial charges |
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Define Lewis Acid and Lewis Base |
Lewis Acid accepts a lone pair of electrons. Lewis Base donates a lone pair of electrons. |
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What is the Octet Rule, and what are some exceptions? |
An atom (other than Hydrogen) will tend to form bonds until it is surrounded by eight valence electrons.
Exceptions include He, Li, Be, or neutral B and Al. |
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What does it mean for an atom to have a high ionization energy? |
It does not lose electrons easily. |
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What is the difference between electron affinity and electronegativity? |
Electronegativity refers to an atom's ability to attract electrons toward itself. Electron affinity is a measure of the energy released when an atom gains an electron (and by logic, the energy required to remove the same electron). High ea = high reactivity. |
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What does it mean for an atom to have a high electron affinity? |
It picks up electrons easily. |
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In which direction on the periodic table does atomic radius increase? |
To the left and down |
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Why does atomic radius decrease when moving to the right of the period table, but increase when moving down the table? The # protons increases in both cases, so why is moving down the table resulting in larger radii versus moving to the right, which causes smaller radii? |
The reason is the difference between # protons as you move from left to right versus top to bottom on the table. As you move left to right, the # protons increases by one at a time. From top to bottom, it increases so significantly that additional shells are added because the atoms become much larger, compared to moving left to right, where all of the atoms have the same principal quantum number. All orbitals that have the same value of n are said to be in the same shell (level).
Thus, the difference lies in the fact that as you move left to right, additional electrons are added to the same shell, whereas from top to bottom, you must add new shells (that are farther away from the nucleus) in order to fit the additional electrons, due to the sheer difference in atomic number from top to bottom. |
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True/False: Electronegativity is inversely related to ionization energy. |
False; it's directly related. |
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In which directions on the periodic table does ionization energy increase/decrease, and why? |
Increases left to right because the atomic radii become smaller, therefore the attraction between protons and electrons are greater, resulting in more energy required to separate electrons from the nucleus.
Decreases top to bottom because the atomic radii increase, resulting in electrons farther away from the nucleus and thus easier to pull away. |
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How are atomic radius and ionization energy related on the period table? |
Inversely |
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What is the formula for formal charge? |
(#Valence E - #Nonbonding - 1/2#Bonding) |
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What's the only factor that can change the rate of a zero-order reaction? |
Temperature, because the concentration of the reactants is irrelevant due to their zero order. |
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What does enthalpy change (deltaH) tell you? |
It is the difference between the potential energy of the products and reactants. Negative enthalpy indicates an exothermic reaction (heat-releasing), while a positive enthalpy indicates endothermic reaction (heat is absorbed). |
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What is the activation energy, and how can it be defined quantitatively for the forward and reverse reactions? |
Minimum energy required for a reaction to occur. It is the potential energy difference between the reaction's activated state and the reactants (for the forward reaction). For the reverse reaction, the difference in potential energy between the activated reaction and the products is the activation energy. Thus, Ea forward is not necessarily equal to Ea reverse. |
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Is the value ∆G positive, negative, or zero when a reaction is spontaneous? |
Negative |
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Is the value ∆G positive, negative, or zero when a reaction is NON-spontaneous? |
Positive |
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When are the coefficients of the reactants/products of a reaction equal to the exponents in the equilibrium constant equation? |
Only when the reaction is balanced. Then the concentrations may be plugged in as their experimental data points, while the exponents represent their balanced values. So if there are .05 moles of a rea1ctant, but the ratio of the reactant to its product is 2 moles per 3 moles product, then 2 is the exponent for the reactant in the equilibrium constant equation. |
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For a balanced reaction at equilibrium, if Keq for the forward reaction is 5, what's Keq for the reverse reaction? Why? |
1/Keq, or 1/5 in this case; Keq is the ratio of products/reactants for the forward reaction, therefore the reverse reaction is the inverse of the forward Keq. |
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What is the difference between standard conditions for a reaction at equilibrium, and standard temperature and pressure? When is each used? |
Standard conditions: 25C (298K) @ 1atm (thermodynamic problems of enthalpy/free energy) STP: 0C (273K) @ 1atm (for ideal gas calculations) |
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State the first law of thermodynamics. |
∆U = Q - W, where U is change in total internal energy of a system, Q is the amount of heat transferred to the system, and W is the amount of work done by the system. |
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What is the equation for heat absorption/release in a given process? |
q = mc∆T, where m is mass, and c is specific heat |
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What is specific heat? |
The amount of energy required to raise one gram or kilogram of a substance by one degC or one Kelvin. |
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What is the specific heat of water? |
One calorie per gram per degC (1c/g˚C) |
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What is the ∆H of a reaction, in terms of the products and reactants? |
∆H(rxn) = H(products) - H(reactants) |
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What is the standard state of a substance? |
It is the most stable form (phase) of the substance under standard conditions (298K and 1atm). |
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What's the difference between the standard state of a substance and Standard Temp and Pressure? |
Standard State conditions are used for thermodynamic calculations. Reference values are 298K (sometimes 273K, only if specified) and 1atm. Standard ehtnalpy, standard entropy, and standard free energy are measured under standard state conditions.
STP is defined at 273K and 1atm, and used for measured gas density and volume using the Ideal Gas Law (PV=nRT).
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OIL RIG
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Oxidation is Loss of e's
Reduction is Gain of e's |
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What is an Adiabatic process? |
A process that occurs without transfer of heat or matter between a system and its surroundings. |
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What does isobaric mean? |
Constant pressure (remember -baric reference to pressure...) |
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What's the difference between heat and temperature? |
Temperature is a scale related to the average kinetic energy of the molecules in a substance.
Heat is the transfer of energy that results from two objects at different temperatures from being put in thermal contact with each other. |
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What does Hess's Law state? |
The total change in the potential energy of a system is equal to the changes in potential energies of the individual steps (reactions) of the process. |
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What is enthalpy? |
A measure of the potential energy of a system found in the intermolecular interactions and bonds of molecules |
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What is entropy? |
A measure of the degree to which energy has been spread out through a system or between a system and its surroundings. It is a ratio of heat transerred per unit Kelvin. |
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When is maximum entropy achieved? |
Equilibrium |
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What is the rate law for a general reaction? |
It is the product of the rate constant, k, and the concentrations of reactants, each raised to some power that is experimentally determined. For example:
For the reaction: A + B -> C, rate = k[A]^x[B]^y
The values of k, x and y need to be calculated. X and y are not the molar coefficients of A and B. To calculate k, first find A and B and respective exponents, then use given rate value (provided in passage) to solve for k. |
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What does the Law of Mass Action state? |
If a system is at eq at a given temp, then the following ratio is constant:
Keq = [products]^x/[reactants]^y
Each product and reactant has a unique exponent value. |
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What is Faraday's constant? |
Charge of one mole of electrons. It is equal to 9.65x10^4 C/mol. (C = Coulombs) |
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What is Effusion?
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Flow of gas particles under pressure from one compartment to another through a small opening.
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What is the volume of one mole of gas at STP?
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22.4L
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When does a gas deviate from ideality?
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At high pressure and low temperature, because the intermolecular attractions increase under these conditions. High pressure forces particles closer together, and low temperature decreases their velocity.
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What is the equation for Partial Pressure?
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Partial Pressure = (mole fraction)x(total pressure)
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True/False: Ionic solids have high melting points, high boiling points, and poor electrical conductivity.
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True; electrical conductivity is high in the molten or aqueous state
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What are the three cubic unit cells?
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1) Simple cubic
2) Body-centered cubic 3) Face-centered cubic |
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What is sublimation?
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when a solid goes directly into the gas phase (bypassing liquid state); dry ice is an example
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What is the triple point?
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It's the point at which the three phases exist at equilibrium.
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What is Raoult's Law?
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Pb = XbP˚b, where Xb is the mole fraction of solvent B in solution, and P˚b is the vapor pressure of B above solvent B.
Only valid for miscible liquids. Liquids that are immiscible are not ideal, and do not follow this law. |
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When a nonvolatile solute is dissolved into a solvent, is the boiling point of the solution higher or lower than that of the solvent?
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Higher
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What is deposition?
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A direct transition from gas to solid (opposite of sublimation).
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What is solvation?
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the electrostatic interaction between solute and solvent molecules
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Is bond formation an endo or exothermic reaction?
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Exothermic, because energy must be lost in order for bonds to become more stable.
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Is the breaking of bonds endo or exothermic?
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Endothermic, because energy must be supplied to the molecular bond in order for it to break.
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Formula for percent composition by mass of solute in solution |
[(mass of solute)/(mass of solution)] x 100%
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Formula for molality
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#moles per kilogram solvent
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Formula for Normality of a solution
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#equivalents of solute per liter of solution
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T/F: The solubility of gases in liquids is directly proportional to the atmospheric pressure.
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True
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What is a Bronsted-Lowry acid and base?
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Bronsted-Lowry Acid: donates hydrogen ions
Brosted-Lowry Base: Accepts hydrogen ions |
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What is the conjugate base of H3O
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H2O
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What is a lewis acid?
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accepts electron pairs (remember: an acid accepts electrons)
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What is a lewis base?
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an electron pair donor
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What is an amphoteric species?
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One that, in the presence of a base, acts like an acid and, in the presence of an acid, acts like a base. Example: H2O
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Value of the water dissociation constant, Kw?
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10^-14 at 298K
This is an equilibrium constant. The value does not change at 298K. |
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Formula for pH
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pH = -log[H+] = log(1/[H+])
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Formula for pOH
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pOH = -log[OH-] = log(1/[OH-])
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What values of Ka and Kb are considered weak acids or bases?
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Kb less than 1.0 is a weak base.
Ka less than 1.0 is a weak acid. |
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What is the relationship between Kw and the acid/base dissociation constants Ka and Kb?
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10^-14 Kw = Ka x Kb
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What's the product of a reaction between a strong acid and strong base?
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A salt and H2O
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Fact
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Acids formed from anions whose names end in -ide (the anion that combines with H+ to form an acid) have the prefix hydro- and end in -ic.
Example: Fluoride's conversion to acid is Hydrofluoric acid. |
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Fact
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Acids formed from oxyanions ending in -ite (less oxygen) will end with -ous acid.
Example: Chlorite's conversion to acid is Chlorous acid |
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Fact
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An anion ends in -ate (more oxygen), then its acid will end with -ic acid.
Example: Perchlorate's acid is Perchloric acid. |
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What is equivalence point in acid-base titration?
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The point at which the number of acid equivalents is equal to the number of base equivalents.
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What is the difference between pKa and pH?
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pKa is a measure of the strength of an acid. The lower the pKa value, the stronger the acid.
pH is a measure of the concentration of acid (H+) in a solution. |
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What's the difference between pKa and Ka?
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pKa = -log(Ka)
Because the right hand side of the equation is always 0 or a negative number, it can be deduced that the larger the Ka value, the smaller the pKa value. Strong acids have very low pKa values (often negative values), and very high Ka values (1,000+). |
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At or below what pKa value is a compound considered to be a strong acid?
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-1.74
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At or above what Ka value is a compound considered to be a strong acid?
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Above 1.0; Ka values above 10^-7 are weakly acidic, and become strongly acidic above 1.0.
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What's the relationship between Ka and pH?
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The larger the Ka value, the more acidic the compound. At Ka > 1, compounds become strongly acidic.
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What are the rules for assigning oxidation numbers?
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1. Oxidation # of free elements is zero.
2. Oxidation # of monoatomic ion (e.g. Na+, Cl-, Fe3+) is equal to charge of ion. 3. Oxidation # of Group 1A is +1. 4. Oxidation # of Group 2A is +2. 5. Oxidation # of Group 7A is -1, except when combined with an element that has higher electronegativity. 6. Oxidation # of Hydrogen is -1 in compounds with less electronegative elements than Hydrogen (groups 1a and 2a). 7. Oxidation # of Oxygen is -2 in most compounds. 8. Oxidation # of a neutral compound is zero. Sum of oxidation #'s in polyatomic ion equals charge of the ion. Example: in SO4^-2, the oxidation # is zero. |
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What is the Effective Nuclear Charge (Zeff), and what is its trend on the periodic table?
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It's the electrostatic attraction (net positive charge) experienced between valence electrons and the nucleus. As the size and positivity of the nucleus increases, the surrounding electrons experience a stronger electrostatic pull. For elements in same period, Zeff increases from left to right.
As elements move down a group, valence electrons are increasingly separated from the nucleus by a greater number of filled energy levels. The result of increased separation is a decrease in electrostatic attraction (Zeff) as outer most electrons are held less tightly. |
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OIL RIG
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Oxidation is Loss of e's
Reduction is Gain of e's |
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What are the 5 steps to balance a redox reaction?
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1. Separate rxn into two half-rxns. 2. Balance the atoms of each half-rxn.3. Balance the charges of each half-rxn. 4. Add the half-rxns. 5. Confirm mass and charges are balanced. |
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Describe the three types of electrochemical cells.
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1. Galvanic cells (voltaic cells)
2. Electrolytic cells 3. Concentration cells Spontaneous rxns occur in galvanic and concentration cells. Nonspontaneous rxns occur in electrolytic cells. For all electrochemical cells, the electrode where oxidation occurs is called the anode. The site of reduction is called the cathode. |
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What is the charge of one electron (in Coulombs)?
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1.6x10^-19
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What is Faraday's constant?
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It is the charge carried by one mole of electrons. One Faraday = 96,487 C.
For practical purposes, use 100,000 C/mol e-. |
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What is the isoelectric point?
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The isoelectric point (pI, pH(I), IEP), is the pH at which a particular molecule carries no net electrical charge.
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What is the Standard reduction potential?
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It is a measure of the tendency of a compound to be reduced. It is defined at 25degC, 1M for each relevant ion, a partial pressure of 1atm for each gas present, and metals in their pure state.
The higher the Ered˚, the greater the tendency of reduction to occur. In galvanic cells, the electrode species with the higher reduction potential is the cathode, and the species with the lower reduction potential is the anode. |
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What's the difference between a spontaneous and non-spontaneous reaction?
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The ∆G of a reaction determines whether it's spontaneous or nonspontaneous. Non-spontaneous reactions require energy (they're generally endothermic). |
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What is the standard electromotive force (emf) of a rxn?
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It's the difference in potential between two half-cells at standard conditions. Determined by adding the standard reduction potential of the reduced species and the standard oxidation potential of the oxidized species.
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T/F: The standard emf of a galvanic cell is negative.
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False; it's positive
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T/F: The standard emf of an electrolytic cell is negative.
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True
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How are ∆G and emf related?
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∆G = -nFEcell
n = # moles electrons exchanged F = Faraday's constant (96,487 C) Ecell = emf of the cell If the rxn takes place under standard conditions, then ∆G = nFE˚cell. |
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What equation is used to determine the concentration of reactive species in an electrochemical cell?
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Nernst equation
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What equation relates emf and Keq?
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∆G = -RTln(Keq), where R = 8.314 J/(K•mol)
[don't confuse with .0821(L•atm)/(mol•K)] |
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T/F: If a redox reaction is spontaneous, then the overall potential must be positive.
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True
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T/F: The higher the Ered˚ (standard reduction potential), the greater the tendency of reduction to occur.
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True; the opposite is also true (lower Ered˚ = lower tendency to be reduced).
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What is the name of group 1 elements on the periodic table? |
Alkali Metals |
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What is the name of group 8 elements on the periodic table? |
Noble Gases |
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What is the name of group 7 elements on the periodic table? |
Halogens |
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What is the name of group 2 elements on the periodic table? |
Alkali Earth Metals |
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What is the conversion of atm/torr/mmHg? |
1.0mmHg = 1.0 torr, and 1.0atm = 760torr = 760mmHg |
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Which gases are diatomic? |
"Have No Fear Of Ice Cold Beer" - Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine, Bromine |
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State Boyle's Law and some exceptions |
The product of the pressure and volume for a gas is a constant for a fixed amount of gas at a fixed temperature. (PV = constant) When #moles or temperature change, Boyle's Law does not apply to the situation. |
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What is the unit for kinetic energy? |
Joules = 1N•m = 1kg•m^2/s^2 |
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What are the two values of the ideal gas constant, R, and their units? |
0.0821 (L•atm)/(mol•K) and 8.3 J/(mol•K) |
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Graham's Law |
The rate of effusion of a gas is inversely proportional to the square root of the mass of its particles. |
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Formula for Kinetic Energy of gas particles
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Ek = (3/2)k•T, where k is the Boltzmann constant |
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The average molecular kinetic energy of Oxygen gas is found to be the same as Neon gas. How does their temperature compare? |
It's the same. The only variable of kinetic energy of gas is temperature. |
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What is Brownian motion? |
all molecules move rapidly in random movements while colliding w/ each other at normal temp; creates the tendency to mix w/ time |
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Difference between open, closed, and isolated systems. |
Open systems can exchange both matter and energy with an outside system. Closed systems exchange energy but not matter with an outside system. Isolated systems can exchange neither energy nor matter with an outside system. |
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Second Law of Thermodynamics |
An isolated system will increase in entropy over time. ∆S >= q/T, where q = heat transfer and T is temperature in K. |
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Formula for Enthalpy |
∆H = U + PV, where U = internal energy; When pressure is constant, the formula is ∆H = q, where q is heat. |
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Equation relating work, pressure and volume. |
∆W = -P∆V, where -P is negative because the pressure is from an external source, and thus when there's a decrease in volume, there is a net positive Work done on the system. |
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Which of the following states of matter has the greatest (most positive) value of ∆S: solid, liquid, aqueous, gas? |
Gas, since there is more disorder than in other matter states. |
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What does a negative ∆S indicate? |
Decrease in entropy (more order being created). Example is a liquid turning into a solid. The particles become more ordered/stabilized. |
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FACT |
A spontaneous process/rxn will result in an increase in entropy. |
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FACT |
∆G is used when a reaction occurs under constant Pressure and Temperature. |
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FACT |
A spontaneous reaction can be both endothermic and exothermic. The spontaneity of the rxn depends on both enthalpy and entropy, so as long as their sum is negative, the ∆G is negative and thus the process is spontaneous.
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What's the difference between endergonic and endothermic, and exergonic vs exothermic? |
Exer/ender- refer to changes in ∆G, while endo/exo refer to changes in ∆H. |
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What's a colloid? |
A colloid is a solution that has particles ranging between 1 and 1000 nanometers in diameter, yet are still able to remain evenly distributed throughout the solution. They don't settle due to gravity. |
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What defines a strong electrolyte? |
Strong electrolytes dissociate completely in water. |
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What does ppm define for aqueous solutions? |
# of mg/L (1mg/L = 1ppm) |
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What is heat of hydration (hydration enthalpy)? |
Enthalpy change when a gaseous solute is dissolved in water. Can be + or -. |
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FACT |
Adding a nonvolatile solute lowers vapor pressure.
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FACT |
The higher the charges of the ions in a salt, the more difficult it is to separate them. |
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Under which conditions is standard reduction potential measured? |
The standard potentials are all measured at 298 K, 1 atm, and with 1 M solutions. |
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What is the standard reduction potential? |
It's the potential difference between the cathode and anode of a cell. |
