Exam 3 Flashcards
Which of the following is the correct rate law for the reaction 2A + B 2C?
a) rate = k[A]
b) rate = k[A][B]
c) rate = k[A]^2 [B]
d) rate = [C]^2 / ([A]^2[B])
e) we cannot determine the rate law from the information given
E. We cannot determine the rate law from the information given
a piece of wood found in an archeological site was found to have only 60% of the carbon-14 found in a living tree. The half-life of carbon-14 is 5730 years. How old is the piece of wood?
a) ~2200 years
b) ~3400 years
c) ~4200 years
d) ~5700 years
e) ~7600 years
c) ~4200 years
When a reaction is at equilibrium
- the value of Q is equal to the value of K
- the rate of the forward reaction is equal to the rate of reverse reaction
- change in G is equal to zero
a) 1
b) 3
c) 1 and 3
d) 2 and 3
e) 1 and 2
f) 1, 2, and 3
f) 1, 2, and 3
What is the pH of a 4.0 M solution of hydrocyanic acid (HCN)? The Ka for HCN is 4.0 x 10^-10
a) 4.0
b) 5.2
c) 4.4
d) 8.8
c) 4.4
N2 (g) + 3 H2 (g) 2 NH3 (g) The system described avoce was found to contain 1.0 mol N2, 3.0 mol H2 and 4.0 mol NH3 in a 1.0 L vessel at equilibrium. What is the value of the equilibrium constant? a) 0.59 b) 0.75 c) 1.3 d) 1.7
a) 0.59
How would the composition of the system, H2 (g) + 3 H2 (g) 2 NH3 (g), at equilibrium change following the addition of H2 (g)?
1. the concentrations of H2 and H2 would increase and the concentration of NH3 would decrease
2. the concentrations of H2 and H2 would decrease and the concentration of NH3 would increase
why?
3. the reaction shifts to the left
4. the reaction shifts to the right
5. more collisions between the reactants will increase the rate of the forward reaction
6. more collisions between the products will decrease rate of the reverse reaction
a) 1 and 3
b) 2 and 4
c) 1 and 4
d) 2 and 5
e) 2 and 4
d) 2 and 5
The equilibrium constant, K = 5 for the reaction 2 NO2 (g) N2O4 (g). If you prepare a mixture of these gases in which [NO2] = 2 M and [N2O4] = 10 M, what will happen?
a) Q = K so the system will not shift
b) Q > K so the system will shift toward the products
c) Q > K so the system will shift towards the products
d) Q
e) Q
when an endothermic reaction is heated:
1. the equilibrium shifts toward the reactants
2. the equilibrium shifts toward the products
because
3. when a system at equilibrium is stressed, the system will shift to counteract that stress
4. the rate of the forward reaction is initially increased more than the rate of the reverse reaction
5. the rate of the reverse reaction is initially increased more than the rate of the forward reaction
a) 1 and 3
b) 1 and 5
c) 2 and 3
d) 2 and 4
d) 2 and 4
which of the following gives information on how far a reaction will progress?
a) the activation energy, Ea
b) the sign of delta G
c) the rate constant, k
d) the sign of delta H system
e) the sign of delta S system
b) the sign of delta G
if the rate = k[B][C] for the reaction A + B + C D, which of the following is true about the reaction mechanism?
a) the reaction mechanism involves exactly one step
b) the reaction mechanism involves at least two steps
c) the reaction mechanism involves exactly two steps
d) the reaction mechanism involves exactly three steps
e) the reaction mechanism could involve one, two, three, or more steps
b) the reaction mechanism involves at least two steps
Calculate the pH of a 0.003 M solution of acetic acid that also contains 0.01 M potassium acetate. The Ka for acetic acid is 1.8 x 10^-5.
a) 4.2
b) 5.3
c) 4.7
d) 7.0
b) 5.3
Which of the following substances could be used with ammonia (NH3) to make a buffer solution
a) NaCl
b) NaOH
c) NH4Cl
d) CH3COOH
c) NH4Cl
An enzyme is a protein that acts as a catalyst. Enzymes work by
a) lowering the energy of the products
b) stabilizing the transition state and lowering the activation energy of the rate determining step
c) increasing the rate of the reaction and shifting the equilibrium in the forward direction
d) changing K for the reaction to make it more favorable
b) stabilizing the transition state and lowering the activation energy of the rate determining step
What is the approximate pH of a 0.10 M solution of sodium acetate? 1. less than 7 2. greater than 7 3. equal to 7 why? 4. the cation of the salt will react with water to produce hydronium ions 5. the anion of the salt will react with water to produce hydroxide ions 6. neither ion will react with water a) 1 and 4 b) 1 and 5 c) 2 and 4 d) 2 and 5 e) 3 and 4
d) 2 and 5
Why does ATP hydrolysis release energy?
a) energy stored in the high energy P-O bonds is released upon hydrolysis
b) energy is released when the high energy P-O bonds are broken
c) energy is released because more energy is released upon forming bonds than is absorbed upon breaking bonds in the hydrolysis process
d) hydrolysis reactions are always exergonic
e) hydrolysis reactions are always exothermic
c) energy is released because more energy is released upon forming bonds than is absorbed upon breaking bonds in the hydrolysis exothermic
Consider the coupled reactions: A + B C D The system has established a steady state equilibrium when
a) the rate of the forward reaction is equal to the rate of the reverse reaction
b) the equilibrium constant is equal to 1
c) adding D to the system shifts the reaction in the reverse direction
d) the rate that C is formed is equal to the rate that C is consumed
d) the rate that C is formed is equal to the rate that C is consumed
