(a) Select all of the correct statements about reaction rates from the choices b
ID: 979713 • Letter: #
Question
(a) Select all of the correct statements about reaction rates from the choices below.
The lower the rate of a reaction the longer it takes to reach completion.
Reaction rate constants increase with increasing temperature.
Solid catalysts increase reaction rates as their surface areas increase.
The rate of a reaction is the same as the rate constant of the reaction.
The slowest step in a reaction is called the rate-determining step.
Reaction rates increase with increasing temperature.
The rate of a slow step has more effect on the overall reaction rate than the rate of a fast step.
Explanation / Answer
The lower the rate of a reaction the longer it takes to reach completion: true
Reaction rate constants increase with increasing temperature: true (because collision between the reactant particles increase)
Solid catalysts increase reaction rates as their surface areas increase: false (catalyst do not affect the reaction rates, it only changes the amount of activation energy)
The rate of a reaction is the same as the rate constant of the reaction: false (A--> B; rate = rate constant*Bn ; n= order of the reaction)
The slowest step in a reaction is called the rate-determining step: true
Reaction rates increase with increasing temperature: true
The rate of a slow step has more effect on the overall reaction rate than the rate of a fast step: True [The slowest step of a chemical reaction determines the rate at which the overall reaction proceeds. There are examples where a reactant that appears in a fast step does not appear in the rate equation. Reactants in the slow step appears in the rate equation
2H2 + 2NO --> N2 + 2H2O
r = k[H2][NO]2
1. 2NO <--> N2O2 (fast)
2. N2O2 + H2 --> N2O + H2O (slow)
3. N2O + H2 --> N2 + H2O (fast)
The second molecule of H2 does not appear in the rate equation because it reacts in the third step, which is a rapid step after the rate-determining step, so that it does not affect the overall reaction rate.]
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