Name:______
Date:______Per. #:______
Chemistry – Unit 7
HW 7.2 – Rate Laws and Kinetic Factors READ pgs. 568-577
1. What is a catalyst? Explain the effect of a catalyst on the rate of a chemical reaction.
2. The reaction for the decomposition of hydrogen peroxide is
2 H2O2(aq) à 2 H2O(l) + O2(g)
List three ways to speed up the rate of decomposition and explain why each is effective based on collision theory.
3. A component of smog is the gas NO. One reaction that controls [NO] is
H2(g) + 2 NO(g) à H2O(g) + N2O(g)
At high temperatures, doubling [H2] doubles the rate of the reaction, while doubling [NO] increases the rate by four times. Write a rate law for this reaction consistent with these data.
4. Use the following chemical equation to answer the questions below:
Mg(s) + 2 H3O+(aq) + 2 Cl–(aq) à Mg2+(aq) + 2 Cl–(aq) + H2(g) + 2 H2O(l)
If 0.048 g of magnesium completely reacts in 20 s, what is the average reaction rate in moles/second over that time interval?
5. a) Determine the overall balanced equation for a reaction that has the following proposed mechanism:, and write an acceptable rate law.
Step 1: B2 + B2 à E3 + D slow
Step 2: E3 + A à B2 + C2 fast
b) What is the intermediate?
c) Give the order of the reaction with respect to each reactant.
d) What is the overall order of the reaction?
6. A chemical reaction is expressed by the balanced chemical equation
A + 2 B à C
Three reaction rate experiments yield the following data:
Trial / [A] (M) / [B] (M) / Initial Rate of formation of C (M/s)1 / 0.20 / 0.20 / 2.0 ´ 10–4
2 / 0.20 / 0.40 / 8.0 ´ 10–4
3 / 0.40 / 0.40 / 1.6 ´ 10–3
a) What is the order of the reaction with respect to A?
b) What is the order of the reaction with respect to B?
c) Determine the rate law for the reaction.
d) Calculate the value of the rate constant, k.
e) If the initial [A] and [B] are 0.30 M, at what initial rate is C formed?
7. A particular reaction is found to have the rate law: R = k[A][B]2. How is the rate affected by each of the following changes?
a) Initial [A] is cut in half.
b) Initial [B] is tripled.
c) [A] is doubled and [B] is cut in half.
8. For each of the following pairs, choose the substance or process that you would expect to
react more rapidly.
a) granulated sugar or powdered sugar
b) zinc in HCl @ 298 K or zinc in HCl @ 320 K
c) ethanol with O2 @ 5 atm or ethanol with O2 @ 1 atm