Practice Reaction Rate in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

The speed at which reactants are converted into products in a chemical reaction, quantified as the change in concentration of a reactant or product per.

How quickly the reaction happens—from instant explosion to years of rusting.

Showing a random 20 of 50 problems.

Example 1

medium
A gas reaction speeds up when the volume is halved at constant temperature. Explain in terms of rate factors.

Example 2

medium
Given initial-rate data: trial 1 [A]=0.10 M, rate=0.020; trial 2 [A]=0.30 M, rate=0.060 M/s. Find the order in A.

Example 3

easy
For the reaction A→B\text{A} \rightarrow \text{B}, A drops by 0.040 M0.040\,\text{M} in 2 s2\,\text{s}. Find the rate.

Example 4

easy
Does crushing a solid into powder speed up or slow down its reaction rate?

Example 5

easy
In 2A→B2\text{A}\rightarrow\text{B}, A disappears at 0.10 M/s0.10\,\text{M/s}. Using coefficients, at what rate does B form?

Example 6

hard
In H2+I2→2HI\text{H}_2 + \text{I}_2 \rightarrow 2\text{HI}, rate =k[H2][I2]=k[\text{H}_2][\text{I}_2]. If both [H2_2] and [I2_2] are doubled, by what factor does rate change?

Example 7

medium
A reaction's rate doubles when temperature rises from 25∘C25^\circ\text{C} to 35∘C35^\circ\text{C}. What approximate empirical rule does this match?

Example 8

easy
Why does increasing temperature speed up a chemical reaction?

Example 9

hard
For the rate law in the previous problem, find kk using trial 1 data.

Example 10

challenge
Two reactions both consume A. Reaction 1 is zero order; reaction 2 is first order in A. As A is depleted, which reaction's rate stays constant, and why?

Example 11

challenge
Initial-rate data: [A]0=0.10, [\text{A}]_0=0.10,\,rate=0.002=0.002; [A]0=0.20, [\text{A}]_0=0.20,\,rate=0.008 M/s=0.008\,\text{M/s}. Find the order in A and kk.

Example 12

challenge
A reaction is first order with k=0.10 s−1k=0.10\,\text{s}^{-1}. If [A]0=0.80 M[\text{A}]_0=0.80\,\text{M}, what is the initial rate, and is the rate at [A]=0.40 M[\text{A}]=0.40\,\text{M} half of it?

Example 13

hard
Two identical zinc samples react with HCl: one in 1 M1\,\text{M} HCl and one in 0.10 M0.10\,\text{M} HCl. Which produces H2_2 faster, and why?

Example 14

easy
What are the SI units of reaction rate when measured by concentration?

Example 15

medium
Over 5 s5\,\text{s}, O2\text{O}_2 in 2H2+O2→2H2O2\text{H}_2+\text{O}_2\rightarrow2\text{H}_2\text{O} drops by 0.10 M0.10\,\text{M}. Find the rate of H2\text{H}_2 disappearance.

Example 16

medium
Activation energy is the minimum energy needed for a successful ____ between reactant particles.

Example 17

medium
For N2+3H2→2NH3\text{N}_2+3\text{H}_2\rightarrow2\text{NH}_3, H2\text{H}_2 is consumed at 0.090 M/s0.090\,\text{M/s}. Find the rate of formation of NH3\text{NH}_3.

Example 18

medium
A first-order reaction has rate constant k=0.050 s−1k = 0.050\,\text{s}^{-1}. What is the initial rate when [A]0=2.0 M[\text{A}]_0 = 2.0\,\text{M}?

Example 19

medium
Why does a catalyst increase reaction rate without being consumed?

Example 20

easy
A reactant concentration drops from 0.80 M0.80\,\text{M} to 0.50 M0.50\,\text{M} over 6 s6\,\text{s}. What is the average rate of disappearance?
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