AP 5.1 Reaction Rates BANK

Which of the following will most likely increase the rate of the reaction represented above?

• Decreasing the temperature of the reaction system

• Adding a heterogeneous catalyst to the reaction system

• Increasing the volume of the reaction vessel using a piston

• Removing some H₂(g) from the reaction system

An experiment is performed to measure the mass percent of CaCO3(s) in eggshells. Five different samples of CaCO3(s) of known mass react with an excess of 2.0MHCl(aq) in identical sealed, rigid reaction vessels. The pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. Since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded.

Which of the following modifications will increase the rate of the reaction the most?

• Using 2.0M CH3COOH(aq) instead of 2.0M HCl(aq)

• Cooling the HCl(aq) to a lower temperature than it was in the original experiment

• Reducing the volume of the reaction vessel

• Using eggshells that are more finely powdered than those used in the original experiment

Two solid reactants of varying particle size are combined in a vessel. Assuming that the same mass of each reactant is used in each case, which of the following represents the conditions that will result in the fastest reaction rate?

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• In the student’s sample the metal pieces were much smaller than those in the other students’ samples.

• The student heated the reaction mixture as the HNO₃(aq) was added.

• The student used a 1.5 M solution of HNO₃(aq) instead of a 15.8 M solution of HNO₃(aq).

• The student used a 3.00 g sample of the mixture instead of the 2.00 g sample that was used by the other students.

A 0.50g sample of Mg(s) was placed in a solution of HCl(aq), where it reacted completely.

In a third experiment, 0.10g samples of Mg(s) are placed in excess HCl(aq) of various concentrations: 0.050M, 0.10M, 0.25M, and 0.50M. The reactions are run in successive order from 0.050M to 0.50M, and the time required for each reaction to go to completion is recorded. As the concentration of HCl(aq) increases from 0.050M to 0.50M, which of the following is the expected result?

• The reaction time increases, and the rate of the reaction decreases.

• The reaction time decreases, and the rate of the reaction increases.

• Both the reaction time and the rate of the reaction increase.

• Both the reaction time and the rate of the reaction decrease.

H₃AsO₄ + 3 I^– + 2 H3O⁺ → H₃AsO₃ + I₃^– + H₂O

The oxidation of iodide ions by arsenic acid in acidic aqueous solution occurs according to the stoichiometry shown above. The experimental rate law of the reaction is:

Rate = k[H₃AsO₄] [I^–] [H₃O⁺]

 

According to the rate law for the reaction, an increase in the concentration of hydronium ion has what effect on this reaction?

• The rate of reaction increases.

• The rate of reaction decreases.

• The value of the equilibrium constant increases.

• The value of the equilibrium constant decreases.

• Neither the rate nor the value of the equilibrium constant is changed.

Step 1: Cl(g) + O₃(g)  →  ClO(g) + O₂(g)

Step 2: ClO(g) + O(g)   →   Cl(g) + O₂(g)

A proposed mechanism for destruction of ozone gas in the stratosphere is represented above. Which of the following is evidence that the mechanism is occurring?

• The presence of Cl(g) increases the rate of the overall reaction.

• The presence of Cl(g) decreases the rate of the overall reaction.

• The presence of Cl(g) increases the equilibrium constant of the overall reaction.

• The presence of Cl(g) decreases the equilibrium constant of the overall reaction.

C₂H₄(g) + H₂(g) →platinum→ C₂H₆(g)

 

C₂H₄(g) is reduced by H₂(g) in the presence of a solid platinum catalyst, as represented by the equation above. Factors that could affect the rate of the reaction include which of the following?

1. Changes in the partial pressure of H₂(g)

2. Changes in the particle size of the platinum catalyst

3. Changes in the temperature of the reaction system

• 3 only

• 1 and 2 only

• 1 and 3 only

• 2 and 3 only

• 1, 2, and 3

5 H₂O₂(aq) + 2 MnO₄^-(aq) + 6 H⁺(aq) → 2 Mn²⁺(aq) + 8 H₂O(l) + 5 O₂(g)

In a titration experiment, H₂O₂(aq) reacts with aqueous MnO₄^-(aq) as represented by the equation above. The dark purple KMnO₄ solution is added from a buret to a colorless, acidified solution of H₂O₂(aq) in an Erlenmeyer flask. (Note: At the end point of the titration, the solution is a pale pink color.)

At a certain time during the titration, the rate of appearance of O₂(g) was 1.0 x 10^-3 mol/(L⋅s). What was the rate of disappearance of MnO₄^- at the same time?

• 6.0 x 10^-3 mol/(L⋅s)

• 4.0 x 10^-3 mol/(L⋅s)

• 6.0 x 10^-4 mol/(L⋅s)

• 4.0 x 10^-4 mol/(L⋅s)

A kinetics experiment is set up to collect the gas that is generated when a sample of chalk, consisting primarily of solid CaCO₃, is added to a solution of ethanoic acid, CH₃COOH. The rate of reaction between CaCO₃ and CH₃COOH is determined by measuring the volume of gas generated at 22^oC and 1 atm as a function of time. Which of the following experimental conditions is most likely to increase the rate of gas production?

• Decreasing the volume of ethanoic acid solution used in the experiment

• Decreasing the concentration of the ethanoic acid solution used in the experiment

• Decreasing the temperature at which the experiment is performed

• Decreasing the particle size of the CaCO₃ by grinding it into a fine powder