Q. In a zero-order reaction, how does the concentration of the reactant affect the rate?
A.
Rate is directly proportional to concentration
B.
Rate is inversely proportional to concentration
C.
Rate is independent of concentration
D.
Rate is proportional to the square of concentration
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Solution
In a zero-order reaction, the rate is constant and does not depend on the concentration of the reactants.
Correct Answer:
C
— Rate is independent of concentration
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Q. In the Arrhenius equation, what does the term 'A' represent?
A.
Activation energy
B.
Frequency factor
C.
Rate constant
D.
Temperature
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Solution
'A' is the frequency factor in the Arrhenius equation, which represents the number of collisions that result in a reaction.
Correct Answer:
B
— Frequency factor
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Q. What effect does increasing the temperature have on the rate of a chemical reaction?
A.
Decreases the rate
B.
Increases the rate
C.
No effect on the rate
D.
Depends on the reaction
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Solution
Increasing the temperature generally increases the kinetic energy of the molecules, leading to more frequent and effective collisions, thus increasing the reaction rate.
Correct Answer:
B
— Increases the rate
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Q. What is the effect of a catalyst on the activation energy of a reaction?
A.
Increases activation energy
B.
Decreases activation energy
C.
Has no effect on activation energy
D.
Changes the reaction mechanism
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Solution
A catalyst lowers the activation energy of a reaction, allowing it to proceed more quickly.
Correct Answer:
B
— Decreases activation energy
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Q. What is the half-life of a first-order reaction dependent on?
A.
Initial concentration
B.
Rate constant only
C.
Both initial concentration and rate constant
D.
Temperature only
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Solution
The half-life of a first-order reaction is independent of the initial concentration and depends only on the rate constant k.
Correct Answer:
B
— Rate constant only
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Q. What is the half-life of a first-order reaction?
A.
Constant and independent of initial concentration
B.
Depends on initial concentration
C.
Increases with time
D.
Decreases with time
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Solution
The half-life of a first-order reaction is constant and independent of the initial concentration of the reactant.
Correct Answer:
A
— Constant and independent of initial concentration
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Q. What is the rate law for a reaction that is first order with respect to A and second order with respect to B?
A.
Rate = k[A][B]
B.
Rate = k[A]^1[B]^2
C.
Rate = k[A]^2[B]^1
D.
Rate = k[A]^2[B]^2
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Solution
The rate law is determined by the order of the reaction with respect to each reactant. For first order in A and second order in B, the rate law is Rate = k[A]^1[B]^2.
Correct Answer:
B
— Rate = k[A]^1[B]^2
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Q. What is the relationship between reaction rate and concentration for a first-order reaction?
A.
Rate is proportional to concentration
B.
Rate is proportional to the square of concentration
C.
Rate is independent of concentration
D.
Rate is inversely proportional to concentration
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Solution
For a first-order reaction, the rate is directly proportional to the concentration of the reactant.
Correct Answer:
A
— Rate is proportional to concentration
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Q. What is the unit of the rate constant k for a second-order reaction?
A.
M
B.
M/s
C.
1/M·s
D.
M^2/s
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Solution
For a second-order reaction, the rate law is Rate = k[A]^2, and the units of k must be 1/(M·s) to ensure that the rate has units of M/s.
Correct Answer:
C
— 1/M·s
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