AP Chem Unit 5

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

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TRA-3.A

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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TRA-3.A

Cu(s) + 4 HNO₃(aq) → Cu(NO₃)₂(aq) + 2 NO₂(g) + 2 H₂O(l)

Each student in a class placed a 2.00 g sample of a mixture of Cu and Al in a beaker and placed the beaker in a fume hood. The students slowly poured 15.0 mL of 15.8 M HNO₃(aq) into their beakers. The reaction between the copper in the mixture and the HNO₃(aq) is represented by the equation above. The students observed that a brown gas was released from the beakers and that the solutions turned blue, indicating the formation of Cu²⁺(aq). The solutions were then diluted with distilled water to known volumes.

In one student’s experiment the reaction proceeded at a much slower rate than it did in the other students’ experiments. Which of the following could explain the slower reaction rate?

• 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.

Tags

TRA-3.A

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.

Tags

TRA-3.A

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.

Tags

TRA-3.A

The initial-rate data in the table above were obtained for the reaction represented below. What is the experimental rate law for the reaction?

2 NO(g) + O₂(g) → NO₂(g)

• Rate = k[NO][O₂]

• Rate = k[NO][O₂]²

• Rate = k[NO]²[O₂]

• Rate = k[NO]²[O₂]²

• Rate = k[NO] / [O₂]

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tra-3.b

The table above shows the results from a rate study of the reaction X + Y → Z. Starting with known concentrations of X and Y in experiment 1, the rate of formation of Z was measured. If the reaction was first order with respect to X and second order with respect to Y, the initial rate of formation of Z in experiment 2 would be

• R/4

• R/2

• R

• 2R

• 4R

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tra-3.b

An experiment was conducted to determine the rate law for the reaction A₂(g) + B(g) → A₂B(g). The table above shows the data collected. Based on the data in the table, which statement is correct?

• Since the rate law can be expressed as rate=k[A₂]², tripling the concentration of A₂ will cause a 9-fold increase in the rate of the reaction.

• Since the rate law can be expressed as rate=k[A₂][B], doubling the concentrations of A₂ and B will quadruple the rate of the reaction.

• Since the rate law can be expressed as rate=k[A₂]²[B], tripling the concentration of A2 while keeping the concentration of B constant will triple the rate of the reaction.

• Since the rate law can be expressed as rate=k[A₂][B]₂, doubling the concentration of B while keeping the concentration of A₂ constant will double the rate of the reaction.

Tags

tra-3.b

S₂O₈²⁻(aq) + 3 I⁻(aq) → 2 SO₄²⁻(aq) + I₃⁻(aq)

In aqueous solution, the reaction represented by the balanced equation shown above has the experimentally determined rate law:

rate=k[S₂O₈²⁻][I⁻]

If the concentration of [S₂O₈²⁻] is doubled while keeping [I⁻] constant, which of the following experimental results is predicted based on the rate law, and why?

• The rate of reaction will remain the same, because k will decrease by half.

• The rate of reaction will double, because the rate is directly proportional to [S₂O₈²⁻].

• The rate of reaction will increase by a factor of four, because two moles of SO₄²⁻ are produced for each mole of S₂O₈²⁻− consumed.

• The rate of reaction will increase by a factor of four, because the reaction is second order overall.

Tags

tra-3.b

The rate law for the reaction of nitrogen dioxide and chlorine is found to be rate = k [NO₂]²[Cl₂]. By what factor does the rate of the reaction change when the concentrations of both NO₂ and Cl₂ are doubled?

• 2

• 3

• 4

• 6

• 8

Tags

tra-3.b