Unit 5- MCQ ?'s

2X+Y2→X2Y2 A chemist is studying the reaction between the gaseous chemical species X and Y2, represented by the equation above. Initial rates of reaction are measured at various concentrations of reactants. The results are recorded in the following table.Based on the information above, determine the initial rate of disappearance of X in experiment 1.

64M/s

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

First order

C12H22O11(aq)+H2O(l)→2C6H12O6(aq) 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 the water molecules.

On the basis of the data in the graph, which of the following best represents the rate law for the catalyzed decomposition of NH3(g) ?

Rate=k

H2(g)+I2(g)→2HI(g) For the reaction between H2 and I2, shown above, the following two-step reaction mechanism is proposed. Step 1: I2⇄2I(fast equilibrium) Step 2: H2+2I→2HI(slow) What is the rate law expression for this reaction if the second step is rate determining?

Rate=k[H2][I2]

2X+Y2→X2Y2 A chemist is studying the reaction between the gaseous chemical species X and Y2, represented by the equation above. Initial rates of reaction are measured at various concentrations of reactants. The results are recorded in the following table. What is the rate law?

Rate=k[X][Y2]

Reaction A: O+O→O2Reaction B: C2H4+C2H4→C4H8Reaction C: CO+O2→CO2+OReaction D: CH3I+Br−→CH3Br+I− 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 diagram above shows the progress of the chemical reaction for the synthesis of ammonia from its elements. The adsorption of the N2 molecules 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?

Ru is a catalyst.

Step 1: ?(slow) Step 2: NO2(g)+F(g)→NO2F(g)(fast) Overall: 2 NO2(g)+F2(g)→2NO2F(g) 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(g)+F2(g)→NO2F(g)+F(g), and the rate law for the overall reaction is rate=k[NO2][F2].

Step 1: H2O2+I−→IO−+H2OStep 2: H2O2+IO−→H2O+O2+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?

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

Step 1: N2O5→NO2+NO3(slow) Step 2: NO2+NO3→NO2+NO+O2(fast) Step 3: NO+N2O5→3 NO2(fast) A proposed reaction mechanism for the decomposition of N2O5(g) 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(g)→4NO2(g)+O2(g), 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(g) and H2(g), 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 trial 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.

CH3I+NaOH→CH3OH+NaI The rate of the reaction represented by the chemical equation shown above is expressed as rate=k[CH3I][NaOH]. Based on this information, which of the following claims is correct?

The rate of the reaction will double if the concentration of CH3I is doubled while keeping the concentration of NaOH constant.

A proposed mechanism for the reaction H2+2IBr→I2+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?

The rate of the reaction will undergo a 4-fold increase in the experiment in which the initial concentrations of both H2 and IBr were doubled.

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(s)+2 HCl(aq)→ZnCl2(aq)+H2(g) Zn(s) reacts with HCl(aq) according to the equation shown above. In trial 1 of a kinetics experiment, a 5.0g piece of Zn(s) is added to 100mL of 0.10MHCl(aq). The rate of reaction between Zn(s) and HCl(aq) is determined by measuring the volume of H2(g) produced over time. In trial 2 of the experiment, 5.0g of powdered Zn(s) is added to 100mL of 0.10MHCl(aq). Which trial will have a faster initial rate of reaction and why?

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

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

Two steps: Step 1: 2X(g)→X2(g)Step 2: X2(g)+Y(g)→X2Y(g)

Bi 83214→Po 84214+e−1 0 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]

Step 1: 2NO⇄(NO)2(fast) Step 2: (NO)2+O2⇄2NO2(slow) The elementary steps in a proposed mechanism for the reaction 2 NO(g)+O2(g)→2NO2(g) 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]

Step 1: 2X(g)⇄X2(g)(fast) Step 2: X2(g)+Y(g)→X2Y(g)(slow) The rate law for the hypothetical reaction 2X(g)+Y(g)→X2Y(g) 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]