AP Chem Kinetics MCQ's

2 X +Y2 → X2Y2 Based on the information above, determine the initial rate of disappearance of X in experiment 1.

64 M/s

The diagram above shows the distribution of molecular energies for equimolar samples of a reactant at different temperatures. Based on the diagram, at which temperature will the reactant be consumed at the fastest rate, and why?

At T4, because a larger fraction of the molecules have an energy that is equal to or greater than the activiation energy.

The two diagrams above represent collisions that take place at the same temperature between a CO molecule and an NO2 molecule. The products are CO2 and NO. Which diagram most likely represents an effective collision, and why?

Diagram 1 represents an effective collision because the two molecules have the proper orientation to form a new C-O bond as long as they possess enough energy to overcome the activation energy barrier.

Based on the graphs above, what is the order of the reaction with respect to N2O5?

First Order

The elementary steps in a proposed mechanism for the decomposition of HCOOH are represented above. Which of the following identifies the catalyst in the overall reaction and correctly justifies the choice?

H2SO4, because it is consumed in the first step of the mechanism and regenerated in a later step.

The chemical equation shown above represents the hydrolysis of sucrose. Under certain conditions, the rate is directly proportional to the concentration of sucrose. Which statement supports how a change in conditions can increase the rate of this reaction?

Increasing the concentration of sucrose will increase the rate of hydrolysis by increasing the frequency of the collisions between the sucrose and water molecules.

The diagram above shows the reaction energy profiles for a reaction with and without a catalyst. Which of the following identifies the reaction energy profile for the catalyzed reaction, and why?

Profile Y, because it introduces a different reaction path that reduces the activation energy.

The catalyzed decomposition of NH3 at high temperature is represented by the equation above. The rate of disappearance of NH3 was measured over time for two different initial concentrations of NH3 at a constant temperature. The data are plotted in the graph below. On the basis of the data in the graph, which of the following best represents the rate law for the catalyzed decomposition of NH3?

Rate=k

The elementary steps in a proposed mechanism for the reaction 2 NO + O2→ 2NO2 are represented by the equations above. Which of the following is the rate law for the overall reaction that is consistent with the proposed mechanism?

Rate=k [NO]2[O2]

For the reaction between H2 and I2 shown above, the following two-step reaction mechanism is proposed. What is the rate law expression for this reaction if the second step is rate determining?

Rate=k[H2][I2]

The two-step mechanism for the chemical reaction NO2 + CO → NO + CO2 is shown above. Which of the following equations is a correct rate law that is consistent with the elementary steps in the mechanism?

Rate=k[NO2]2

In the presence of NO, the decomposition proceeds in two elementary steps, as represented by the following mechanism. Based on the information, which of the following is the rate law?

Rate=k[O3][NO]

The rate law for the hypothetical reaction 2 X + Y→ X2Y is consistent with the mechanism shown above. Which of the following mathematical equations provides a rate law that is consistent with this mechanism?

Rate=k[X]2[Y]

2 X + Y2 → X2Y2 Given the information above, which of the following is the experimental rate law?

Rate=k[X][Y2]

The equations shown above represent four elementary reactions. Which of the following identifies the reaction in which the number of successful collisions and reaction rate are independent of the orientation of the reactants and explains why?

Reaction A, because the electron clouds of the O atoms are distributed symmetrically.

The overall reaction represented above is proposed to take place through two elementary steps. Which of the following statements about the chemical equation for step 1 and the rate law for the overall reaction is correct?

The chemical equation for step 1 is NO2 + F2→ NO2F + F, and the rate law for the overall reaction is rate=k[NO2][F2]

The mechanism for a chemical reaction is shown above. Which of the following statements about the overall reaction and rate laws of the elementary reactions is correct?

The chemical equation for the overall reaction is 2H2O2 → 2H2O + O2, and the rate law for elementary step 1 is rate=k[H2O2][I].

A proposed reaction mechanism for the decomposition of N2O5 is shown above. Based on the proposed mechanism, which of the following correctly identifies both the chemical equation and the rate law for the overall reaction?

The chemical equation for the overall reaction is 2N2O5→ 4NO2 + O2, and the rate law is rate=k[N2O5]

The information in the data table above represents two different trials for an experiment to study the rate of the reaction between NO and H2, as represented by the balanced equation above the table. Which of the following statements provides the correct explanation for why the initial rate of formation of N2 is greater in trial 2 than in trail 1? Assume that each trial is carried out at the same constant temperature.

The frequency of collisions between reactant molecules is greater in trial 2 than it is in trial 1.

A second chemist repeated the three experiments and observed that the reaction rates were considerably greater than those measured by the first chemist even though the concentrations of the reactants and the temperature in the laboratory were the same as they were for the first chemist. Which of the following is the best pairing of a claim about a most likely cause for the greater rates measured by the second chemist and a valid justification for that claim?

The second chemist must have added a catalyst for the reaction, thus providing a different reaction pathway for the reactant particles to react with an activation energy that was lower than that of the uncatalyzed reaction in the first chemist's experiments.

Zn reacts with HCl according to the equation shown above. In trial 1 of a kinetics experiment, a 5.0g piece of Zn is added to 100mL of 0.10 M HCl. The rate of reaction between Zn and HCl is determined by measuring the volume of H2 produced over time. In trial 2 of the experiment, 5.0g of powdered Zn is added to 100mL of 0.10 M HCl. Which trial will have a faster initial rate of reaction and why?

Trial 2, because the sample of Zn has a greater surface area for the reaction to take place.

Bismuth-214 undergoes first-order radioactive decay to polonium-214 by the release of a beta particle, as represented by the nuclear equation above. Which of the following quantities plotted versus time will produce a straight line?

ln[Bi]