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128 Cards in this Set
- Front
- Back
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What is defined as the amount of a substance that has the same number of particles as exactly 12.0 grams of the isotope carbon-12?
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mole
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What is Avogadro's number?
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6.02*10^23
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What is the relationship between 44 amu and 44 grams of CO2? |
44 amu refers to a single molecule of CO2 44 grams refers to a mole of CO2 |
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How many particles are in 0.5 moles?
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3.01*10^23
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How many particles are in 2 moles? |
1.204*10^24
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What is the simplest whole number ratio of atoms in a compound? |
empirical formula
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What is the actual whole number ratio of atoms in a molecule of a compound? |
molecular formula
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When given only percent compositions, how can the empirical formula of a compound be determined?
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by assuming there are 100 g of compound
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What is the density of a gas? |
molar mass/V
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What does not result in the product of new substances?
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physical change
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What involves the conversion of the original chemicals into different products? |
chemical change/reaction
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Are phase changes chemical or physical changes?
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physical
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What does Δ mean in a chemical equation? |
heat
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What are five words that indicate chemical changes/reactions?
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rusting decomposing oxidizing forming burning |
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What is a synthesis or combination reaction? |
A + B -> C
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What are seven elements that exist in diatomic form? |
H2 O2 N2 Cl2 Br2 I2 F2 |
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What is a decomposition reaction? |
C -> A + B
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What are the two most common ways to accomplish decompositions? |
add heat pass an electric current through the liquid or aqueous form of the substance |
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What is a single displacement reaction? |
A + BC -> AC + B
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What is a replacement reaction? |
A + BC -> AC + B
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What are most single displacement reactions also?
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oxidation-reduction reactions
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In a single displacement reaction, what does a metal displace? What does a nonmetal displace? |
metal, nonmetal |
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What is a double displacement reaction? |
AB + CD -> AD + CB
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What are metathesis reactions?
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AB + CD -> AD + CB
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What is produced in a combustion reaction? |
CO2 H2O |
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What is produced in an incomplete combustion? |
CO and/instead of CO2
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What only show the ions that undergo changes in a reaction? |
net ionic equations
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What are neutralization reactions? |
acid + base -> salt + water
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What are oxidation and reduction reactions?
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gaining and losing of electrons
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What is the oxidation number of oxygen?
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-2, except in peroxides when it is -1
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Can oxidation and reduction occur separately?
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no
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How can redox reactions be balanced?
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half-reaction method, adding water/H+ as necessary and adjusting with OH- at the end if basic
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What is a disproportionation reaction? |
special type of redox reaction in which the same element is both oxidized and reduced
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What are five common spectator ions? |
nitrate sodium potassium ammonia acetate |
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Does each side of a chemical equation need to have the same total charge?
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yes
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What is a quantitative method of determining the concentration of an unknown solution by its reaction with a solution of known concentration?
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titration
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What is the equation for percent yield? |
(actual yield/theoretical yield)*100
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What is heat?
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total thermal energy
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What is heat transfer due to? |
temperature differences
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Does heat transfer require an input of work? Explain.
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No, heat spontaneously moves from a higher-temperature system to a lower-temperature system.
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What kind of system can exchange heat with the surroundings but cannot exchange matter? |
closed
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What kind of system can exchange both heat and matter with the surroundings?
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open
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What does a state function depend on? |
current conditions of a system and not on how those conditions were reached (the path used)
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What does the law of conservation of energy state? |
energy is neither created nor destroyed, but it can be converted from one form to another
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How many joules is one calorie equal to? |
4.18
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What is the heat content of a system at a constant pressure?
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enthalpy
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What is enthalpy symbolized as?
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H
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How can the enthalpy change for a reaction be determined? |
product enthalpies - reactant enthalpies
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What is the standard enthalpy of formation for any pure element in its nature state? |
0
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What is Hess's Law of heat summation?
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enthalpies of chemical reactions can be added to give enthalpies for new reactions
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What is the average amount of energy required to break one mole of a specific bond type in the gas phase?
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bond energy
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Are bond energies positive or negative? Why?
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Positive, energy is needed to break a bond.
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What is a device used to measure temperature changes in the surroundings during a chemical reaction? |
calorimeter
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What is the significance of a calorimeter being a thermally isolated system?
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The summation of all the heat components add up to zero.
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What is the heat capacity of a substance?
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amount of heat required to raise the temperature of the substance by 1 degree Celsius
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What is the specific heat capacity of a substance?
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amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius
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What is the equation for heat with a known heat capacity but an unknown mass? |
q = C*ΔT
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What is the equation for heat when mass is known?
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q = m * Cp (specific heat capacity) * ΔT
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If the water in a calorimeter rises by 15 degrees Celsius, what is the temperature change in the calorimeter?
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15 degrees
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What is a device used to measure the heat of combustion of a compound, typically a fuel?
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bomb calorimeter
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What are the units for molar heat of combustion?
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J/mol
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What is the tendency of nature to disperse energy? |
entropy
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What is the equation for entropy change and why? |
S(products) minus S(reactants), state function
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At a given temperature, which state of matter has the highest entropy?
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gas
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How can the natural tendency of entropy to increase be overcome?
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by adding work to the system
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When will a chemical system be at its maximum entropy?
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at equilibrium, its state of minimum energy
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Do larger or smaller molecules have greater entropy? |
larger
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Does entropy increase or decrease when the number of moles of gas increases?
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increase
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Does entropy increase or decrease when precipitates form? |
decrease
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What tends to be minimized and what tends to be maximized in chemical processes?
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energy, entropy
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What is the Gibbs free energy equation?
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ΔG = ΔH - TΔS
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What does Gibbs free energy represent? |
maximum amount of work that a system can do
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What common state function must two objects in thermal equilibrium share? |
temperature
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How do heat and temperature relate to thermal energy?
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Temperature is the average thermal energy of molecules; heat is the total thermal energy of molecules.
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What occurs at absolute zero? (2)
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not even atoms move entropy of a perfect crystal is 0 |
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How can heat be transferred between objects? (3) |
conduction convection radiation |
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Do all heat transfers involve energy going from a hotter to a colder object? Why or why not?
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Yes, entropy
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What is the transfer of heat via molecular collisions? |
conduction
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What is the transfer of energy via the motion of fluids (liquids or gases)? |
convection
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Why does convection occur?
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differences in pressure or density
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What is energy transfer via electromagnetic waves? |
radiation
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What is heat of fusion?
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energy change associated with the melting or freezing of a substance
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What is heat of vaporization?
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energy change associated with the boiling of a liquid
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What equation should be used to determine the final temperature of water after ice is added?
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Q(melt of the ice) + Q(warming up melted ice) + Q(cooling down warm water) Q(melt of the ice) = Hfus*mass Q(warming up melted ice) = m*Cp*(Tf-Ti, Ti=the temperature it melted at) Q(cooling down warm water) = m*Cp*(Tf-Ti, Ti = the starting temperature of water) |
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What is a transfer of a form of energy other than heat?
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work
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What is PV work?
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the expansion of gas
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What makes a heat engine more efficient? |
greater difference between the hot and cold temperatures
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What does adiabatic mean?
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no exchange of heat takes place
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What is the study of the rates of reactions and the factors that affect these rates? |
kinetics
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What is the state in which a reversible chemical reaction shows no net change in the concentration of any chemical species?
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equilibrium
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When does equilibrium occur?
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when forward and reverse reaction rates are equal to each other
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What does collision theory state must be true in order for a chemical reaction to occur between two (or more) molecules?
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Molecules must collide with the proper orientation and have enough energy to break the bonds of the reactants.
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What is an effective collision?
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Collision that results in a chemical reaction.
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What are the most common units for describing the rates of chemical reactions?
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M/s
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How can the rate of aA + bB -> cC + dD be described?
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-1Δ[A]/aΔt = -1Δ[B]/bΔt = 1Δ[C]/cΔt = 1Δ[D]/dΔt
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What is activation energy?
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minimum energy of collision required for bonds to be broken and new substances to be formed
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What is a mathematical expression that shows how the rate of a chemical reaction depends on the concentrations of the reactants?
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rate law
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What is the general rate law of A + B + C -> D?
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rate =k([A]^m)([B]^n)([C]^p) m, n, p = orders |
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How can rate constant k be determined?
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By substituting values from any one trial.
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What graph of a zero-order reaction gives a straight line and what is its slope?
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[reactant] versus time, -k
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What graph of a first-order reaction gives a straight line and what is its slope?
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ln [A] versus time, -k
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What order reactions are radioactive decay and growth of bacteria?
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first
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What graph of a second-order reaction gives a straight line and what is its slope?
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1/[A] versus time, k
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How can the concentration of a reactant be calculated for a first-order reaction?
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[A]t = [A]0 * e^-kt
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What is the relationship between the half-life of a first-order reaction and its rate constant? |
t(1/2) = 0.693/k
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What is the slowest step in a reaction mechanism called?
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rate-determining/limiting step
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How do catalysts affect the rate constant?
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increase
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How do catalysts affect the relative amounts of products and reactants at equilibrium?
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They don't.
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What is a homogenous catalyst?
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exists in the same phase as the reactants
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What is the reactant for which an enzyme has high specificity?
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substrate
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How do enzymes act?
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by making molecules adopt the most efficient orientation for reactions
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What is dynamic equilibrium?
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reaction directions are opposite and the rates are equal
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What is the equilibrium constant for Aa + Bb <-> Cc + Dd?
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Keq = ([C]^c * [D]^d)/([A]^a * [B]^b)
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What is Kp?
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equilibrium constant in terms of partial pressures
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Are all reactants and products included in Keq? Why or why not?
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No, solids and liquids are excluded because their concentrations remain constant.
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What measures reactant and product concentrations at any point in the reaction (not necessarily at equilibrium) and what is its symbol?
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reaction quotient Q
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What will happen when Q is greater than Keq?
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The reverse reaction will predominate to produce more reactants.
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What will happen if Q is less than Keq?
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The forward reaction will dominate to produce more products.
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What direction does a chemical system shift when pressure is increased?
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to the side with fewer moles of gas
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How do inert gases affect partial pressures?
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They don't.
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Does a catalyst lower the activation energy in the forward or reverse direction?
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both
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At room temperature, 1 atm of pressure, and 1 M solutions, what is the relationship between Keq and ΔG?
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If Keq is negative, G is positive and vice versa.
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If Keq is positive, is the reaction spontaneous?
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yes
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If Keq is negative, is the reaction spontaneous?
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no
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If Keq = 0, is the reaction spontaneous?
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DNA
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What kind of control is a reaction whose product formation is governed by the relative energies of the products and reactants under?
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thermodynamic
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What kind of control is a reaction whose product formation is governed by the activation energies of the possible reactions under?
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kinetic
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What pathway is taken: the faster or the more energetically favorable? Why?
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faster, lower activation energy
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