Chapter 9: Reaction Kinetics

The experimentally determined rate law for the reaction below,

2 NO(g)   +   2 H₂(g)     →     N₂(g)   +   2 H₂O(g)

is rate = k[NO]²[H₂]. If the concentration of H₂ is doubled, predict what will happen to the reaction rate?

• The reaction rate is quadrupled

• The reaction rate is doubled

• The reaction rate is remain the same

• The reaction rate is tripled

Answer explanation

The order of reaction with respect to H₂ is first order. So, when the concentration is doubled, the rate of reaction will also doubled.

Consider the reaction examined below:

P   +   Q     →     R              Rate  =  k[P]²

If the concentration of Q is doubled, the rate of disappearance of Q _______, whereas if the concentration of P is doubled, the rate of disappearance of Q _______.

• does not change; does not change

• increases by a factor of two; increases by a factor of two

• increases by a factor of four; increases by a factor of two

• does not change; increases by a factor of four

Which of the following is the unit of the rate constant for the following reaction?

CHCl₃(g)  +  Cl₂(g)   →   CCl₄(g)  +  HCl(g)                Rate   =   k[CHCl₃][Cl₂]^½

• M^–½s^–1

• M^–½s^–½

• M^½s^–1

• M^–1s^–1

The decomposition of dinitrogen pentoxide, N₂O₅ to dinitrogen tetraoxide, N₂O₄ and oxygen gas, O₂ is as follows:

2 N₂O₅(g)     →     2 N₂O₄(g)   +  O₂(g)

The initial concentration of N₂O₅ is 0.9736 M. After 9.30 minutes, its concentration is reduced to 0.9033 M. Calculate the average rate of this reaction in the period of time.

• 1.82 x 10^-3 M min^-1

• 1.72 x 10^-3 M min^-1

• 7.56 x 10^-3 M min^-1

• 7.38 x 10^-3 M min^-1

Hydrogen peroxide, H₂O₂ decomposes to water and oxygen gas according to the following equation.

H₂O₂(aq)     →     H₂O(l)   +   ½ O₂(g)

Which of the following will NOT increase the rate of decomposition of hydrogen peroxide?

• Raise the temperature

• Add catalyst

• Increase the concentration of hydrogen peroxide

• Increase the volume of the container

Hydrogen peroxide, H₂O₂ decomposes to water and oxygen gas according to the following equation.

H₂O₂(aq)     →     H₂O(l)   +   ½ O₂(g)

Which of the following will NOT increase the rate of decomposition of hydrogen peroxide?

• Raise the temperature

• Add catalyst

• Increase the concentration of hydrogen peroxide

• Increase the volume of the container

Which of the following statement is TRUE about adding catalyst in a reaction?

• Catalyst participates in the reaction.

• Catalyst changes the concentration of reactant(s).

• Addition of catalyst always decreases the rate of reaction.

• Addition of catalyst lowers the activation energy for the reaction.

Which of the following statement is TRUE about adding catalyst in a reaction?

• Catalyst participates in the reaction.

• Catalyst changes the concentration of reactant(s).

• Addition of catalyst always decreases the rate of reaction.

• Addition of catalyst lowers the activation energy for the reaction.

• Rate  =  k[NO]²[H₂]²

• Rate  =  k[NO]²[H₂]

• Rate  =  k[NO][H₂]²

• Rate  =  k[NO][H₂]

Answer explanation

use the initial rate method to answer this question :)

At a certain time in a reaction, substance X is disappearing at a rate of 4.0 x 10^-2 M s^-1, substance Y is appearing at a rate of 2.0 x 10^-2 M s^-1, and substance Z is appearing at a rate of 6.0 x 10^-2 M s^-1.

Which of the following could be the stoichiometry for the reaction being studied?

• 2X + Y →    3 Z

• X → 2Y + 3 Z

• 2X → Y + 3 Z

• X + 2Y →    3 Z

Answer explanation

The order of reaction with respect to H₂ is first order. So, when the concentration is doubled, the rate of reaction will also doubled.