AP Chem Unit 5 MCQ Key

B: First Order

2N(2)O(5) -- 4NO(2) + O(2) Based on the graphs above, what is the order of the reaction with respect to N(2)O(5)?

A: Rate = k

2NH(3) catalyst---N(2) + 3H(2) On the basis of the data in the graph, which of the following best represents the rate law for the catalyzed decomposition of NH(3)?

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

2NO + 2H(2) -- N(2) + 2H(2)O The information in the data table above represents wo different trials for an experiment to study the rate of the reaction between NO and H(2), 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 N(2) is greater in trail 2 then in trial 1? Assume that each trial is carried out at the same constant temperature.

A: Rate= k[X] [Y(2)]

2X + Y(2) -- X(2)Y(2) A chemist is studying the reaction between the gaseous chemical species X and Y(2), represented by the equation above. Initial rates of reaction are measured at various concentration of reactants. The results are recorded in the following table. Given the information in the table above, which of the following is the experimental rate law?

C: The rate of the reaction will undergo a 4-fold increase in the experiment in which the initial concentrations of both H(2) and IBr were doubled.

A proposed mechanism for the reaction H(2) + 2IBr --- I(2) + 2HBR is shown above. Two experiments were performed at the same temperature but with different initial concentrations. Based on this information, which of the following statements is correct?

B: The chemical equation for the overall reaction is 2N(2)O(5) --- 4NO(2) + O(2), and the rate law is rate = k [N(2)O(5)]

A proposed reaction mechanism for the decomposition of N(2)O(5) 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?

B: Rate = k[NO(2)]^2

A proposed two-step mechanism for the chemical reaction NO(2) + CO --- NO + CO(2) is shown above. Which of the following equations is a correct rate law that is consistent with the elementary steps in the mechanism?

C: 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.

A second chemist repeated the three experiments and observed hat 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 the claim about a most likely cause for the greater rates measured by the second chemist and a valid justification for that claim?

C: 64 M/s

Based on the information above, determine the initial rate of disappearance of X in experiment 1.

C: In[Bi]

Bismuth-214 undergoes first-order radioactive decay to polomium-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?

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

C(12)H(22)O(11) + H(2)O -- 2C(6)H(12)O(6) The chemical equation shown above represents the hydrolysis of sucrose. Under certain conditions, the rate is directly proportional to the concentration of sucrose. Which statements supports how a change in conditions can increase the rate of this reaction?

C: The rate of the reaction will double if the concentration of CH(3)I is doubled while keeping the concentration of NaOH constant.

CH(3)I + NaOH -- CH(3)OH + NaI The rate of the reaction represented by the chemical equation shown is expressed as rate= k[CH(3)I] [NaOH]. Based on this information, which of the following claims is correct?

C: Rate = k [H(2)] [I(2)]

H(2) + I(2) --- 2HI What is the rate law expression for this reaction if the second step is rate determining?

A: Rate = k[O(3)] [NO]

O(3) + O --- 2O(2) Based on the information, which of the following is the rate law?

C: The cemical equation for the overall reaction is 2H(2)O(2) --- 2H(2)O + O(2), and the rate law for elementary step 1 is rate = k [H(2)O(2)] [I^-].

Step 1: H(2)O(2) + I^- --- IO^- + H(2)O Step 2: H(2)O(2) + IO^- --- H(2)O + O(2) + I^- 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?

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

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

A: Ru is a catalyst

The diagram above shows the progress of the chemical reaction for the synthesis of ammonia from its elements. The absorption of the N(2) molecule on the surface of Ru weakens the triple bond between the two N atoms. Based on the diagram, what is the role of Ru in this process?

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

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?

A: H(2)SO(4), because it is consumed in the first step of the mechanism and regenerated in a later step.

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?

C: rate = k[NO]^2 [O(2)]

The elementary steps in a proposed mechanism for the reaction 2NO + O(2) --- 2NO(2 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?

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

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?

A: The chemical equation for step 1 is NO(2) + F(2) ---NO(2)F + F, and the rate law for the overall reaction is rate = k[NO(2] [F(2)].

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?

D: 3 big circles 1 and 2 are gray, 3 is black

The proposed mechanism for the reaction involves the three elementary steps represented by the particle models shown above. On the basis of this information, which of the following models represents and intermediate in the overall reaction?

C: rate = k [X]^2 [Y]

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

B: 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.

The two diagrams above represent collisions that take place at the same temperature between a CO molecule and an NO(2) molecule. The products are CO(2) and NO. Which diagram mostly likely represents an effective collision, and why?

D: Two Steps Step 1: 2 X --- X(2) Step 2: X(2) + Y --- X(2)Y

Which of the following best describes the elementary step(s) in the reaction mechanism represented in the diagram above?

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

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