Chemical Kinetics Unit Test Review

Given the reaction mechanism below:

1. B₂ + 2A --> A₂B + B⁺ (slow)

2. A₂B + C --> A₂ + CB (fast)

Which of the following rate laws agree with the proposed reaction mechanism?

• Rate=k[B]²[A₂]

• Rate=k[A]²[B₂]

• Rate=k[B₂][A]²[C]

• Rate=k[A₂B][C]

Tags

NGSS.HS-PS1-5

Consider the reaction mechanism given below:

1. NO + O₃ --> NO₂ + O₂

2. O₃ --> O₂ + O

3. NO₂ + O --> NO + O₂

Which of the following correctly identifies the role of NO and explains why?

• NO is a catalyst. In a reaction mechanism, catalyst first appear as a product and leave as a reactant.

• NO is a intermediate. Intermediates are formed as a result of a fast initial step.

• NO is a intermediate. Intermediates appear as a reactant and is released as a product in a later step.

• NO is a catalyst. The presence of NO increases the rate of the reaction.

A catalyst always...

• Creates more intermediates in a reaction mechanism.

• Increases the rate of a chemical reaction.

• Results in fewer elementary steps and therefore proceeds at a faster rate.

• Increases the activation energy.

Answer explanation

The use of a catalyst results in a faster reaction rate by providing the reaction an alternative pathway with a LOWER activation energy.

Tags

NGSS.HS-PS1-5

2X₂ + 2BY --> 2X₂Y + 2B

The reaction shown above has the rate law expression

Rate=k[X]²

Which of the following will increase the rate of the chemical reaction?

• Adding a catalyst

• Lowering the temperature of the reaction

• Decreasing the pressure

• Increasing the concentration of X₂

Tags

NGSS.HS-PS1-5

For the reaction shown below, the rate of disappearance of O₂ is 8.6 x 10^-9 M/s . At what rate will [CO₂] change over the same time period?

CH₄ + 2O₂ --> CO₂ + 2H₂O

• (8.6x10^-9M/s)(2/1)

• (8.6x10^-9M/s)

• (8.6x10^-9M/s)(1/2)

• (8.6x10^-9M/s)(2/2)

For a certain chemical reaction, the order with respect to the reactant CH₄ is first order. How would the rate change if the concentration of CH₄ is quadrupled?

• The rate would increase by a factor of 4

• The rate would increase by a factor of 2

• The rate would increase by a factor of 1

• The rate would remained unchanged.

Tags

NGSS.HS-PS1-5

Which of the following statements is TRUE regarding this Maxwell Boltzmann distribution curve?

• The activation energy is higher for temperature 1 than temperature 2.

• The reaction rate is higher for temperature 1.

• More molecules in temperature 1 have a greater average kinetic energy than seen in temperature 2.

• More molecules react in temperature 2 than in temperature 1.

Tags

NGSS.HS-PS1-5

Given below is the reaction mechanism for a certain chemical reaction. Which of the following gives the overall balanced equation and the correct rate law from the molecularity of the step indicated?

1. NO + O₃ --> NO₂ + O₂

2. O₃ --> O₂ + O

3. NO₂ + O --> NO + O₂

• NO₂ + O -> 2O_2;

  Step 3: Rate=k[NO]²[O]

• 2O₃ -> 3O₂

  Step 1: Rate=k[NO][O₃]

• 2NO + 2O₃ -> 2NO₂ + 2O₂

  Step 3: Rate=k[NO₂][O]

Tags

NGSS.HS-PS1-2

NGSS.HS-PS1-5

A reaction has the rate law given below. Determine which of the following correctly predicts the change in the rate of the reaction based on the change in concentration of that reactant. Assume all other reactants remain the same.

Rate=k[P]⁰[S]²[R]¹

• A doubling of concentration R, results in a quadrupling of the reaction rate.

• A doubling of concentration S, results in a quadrupling of the reaction rate.

• A doubling of concentration P, results in a doubling of the reaction rate.

• A doubling of concentration R, results in the halving of concentration P.

Tags

NGSS.HS-PS1-5

Why does a higher temperature increase the rate of a reaction?

• it increases both the frequency and energy of particle collisions
• it only increases the frequency of particle collisions
• it only increases the energy of particle collisions
• it reduces the activation energy of the reaction

Tags

NGSS.HS-PS1-5