AP Chemistry Unit 5 Kinetics

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

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NGSS.HS-PS1-5

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.

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X → products

Pure substance X decomposes according to the equation above. Which of the following graphs indicates that the rate of decomposition is second order in X ?

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The isomerization of cyclopropane to propylene is a first-order process with a half-life of 19 minutes at 500^oC. The time it takes for the partial pressure of cyclopropane to decrease from 1.0 atmosphere to 0.125 atmosphere at 500^oC is closest to

• 38 minutes

• 57 minutes

• 76 minutes

• 152 minutes

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NGSS.HS-PS1-5

X₂ + Y₂ → X₂Y₂

rate = k[X₂]

A reaction and its experimentally determined rate law are represented above. A chemist proposes two different possible mechanisms for the reaction, which are shown. Based on the information, which of the following is true?

• Only mechanism 1 is consistent with the rate law.

• Only mechanism 2 is consistent with the rate law.

• Both mechanism 1 and mechanism 2 are consistent with the rate law.

• Neither mechanism 1 nor mechanism 2 is consistent with the rate law.

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When free Cl(g) atoms encounter O₃₍g) molecules in the upper atmosphere, the following mechanism shown is proposed to occur. Which of the following reaction energy profiles best corresponds to the proposed mechanism?

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NGSS.HS-PS1-2

NGSS.HS-PS1-4

The particle models shown above represent a proposed two-step mechanism for the destruction of ozone (O₃) in the upper atmosphere. Based on the models, which of the following represents a species that acts as a catalyst for the reaction?

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NGSS.HS-PS1-6

The proposed rate-determining step for a reaction is

2 NO₂(g) → NO₃(g)+NO(g)

The graph above shows the distribution of energies for NO₂(g) molecules at two temperatures. Based on the graph, which of the following statements best explains why the rates of disappearance of NO₂(g) are different at temperature 2 and temperature 1 ?

• NO₂(g) is consumed at a faster rate at temperature 2 because more molecules possess energies at or above the minimum energy required for a collision to lead to a reaction compared to temperature 1.

• NO₂(g) is consumed at a faster rate at temperature 2 because the molecules have a wider range of energies allowing for a better orientation during a collision compared to temperature 1.

• Fewer NO₂(g) molecules have a relatively high energy at temperature 1, which favors collisions between molecules rather than between the molecules and the container, leading to a faster rate of disappearance compared to temperature 2.

• More NO₂(g) molecules have a relatively low energy at temperature 1, which increases the number of effective collisions taking place and the rate of disappearance compared to temperature 2.

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A mechanism for the decomposition of ozone

2 O₃ → 3 O₂

is shown. What is the molecularity for the first and second elementary reactions?

• 2 and 2

• 2 and 3

• 1 and 2

• 1 and 1

Cl⁻(aq) + ClO⁻(aq) + 2 H⁺(aq) → Cl₂(g) + H₂O(l)

What effect will increasing [H⁺] at constant temperature have on the reaction represented above?

• The activation energy of the reaction will increase.

• The activation energy of the reaction will decrease.

• The frequency of collisions between H⁺(aq) ions and ClO⁻(aq) ions will increase.

• The value of the rate constant will increase.

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NGSS.HS-PS1-5