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AP Chemistry Unit 5.2: Rate Laws

Practice AP Chemistry Unit 5.2 questions on using initial-rate data to determine reaction orders, write rate laws, calculate k and plan controlled kinetics experiments.

Syllabus
Effective Fall 2025
Course
AP Chemistry

Exam points

  • Use thermodynamic relationships to compare reaction favorability, entropy, enthalpy, and free-energy changes.
  • Calculate or interpret ΔG°, ΔH°, ΔS°, equilibrium constants, and temperature effects from reaction data.

Covered syllabus points

5.2.A—Represent experimental data with a consistent rate law expression

5.2 Introduction to Rate Law question 1

[Maximum number: 3]

Answer the following questions about ascorbic acid (vitamin C).

Question (a)

(a)

Dehydroascorbic acid (DHAsc) can be produced by reacting ascorbic acid with the triiodide

ion, I3−\mathrm{I}_{3}{ }^{-}, as represented by the following equation.

HAsc+I3−→DHAsc+3I−+2H+\mathrm{HAsc}+\mathrm{I}_{3}^{-} \rightarrow \mathrm{DHAsc}+3 \mathrm{I}^{-}+2 \mathrm{H}^{+}

The student runs three trials of the reaction with different initial concentrations of HAsc and

I3−\mathrm{I}_{3}{ }^{-}, producing the following data.

Table for Question (a) — AP Chemistry
[ 3 ]

Question (i)

(i)

The rate law for the reaction is rate =k[HAsc][I3−]=k[\mathrm{HAsc}]\left[\mathrm{I}_{3}{ }^{-}\right]. Explain how the data in the table

support the conclusion that the reaction is first order with respect to [HAsc].

[ 1 ]

Question (ii)

(ii)

Calculate the value of the rate constant, k, for the reaction. Include units with your

answer.

[ 2 ]
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