Chemical Kinetics

For a first-order reaction with a half-life of 30 minutes, what fraction of reactant remains after 90 minutes?

• 1/2

• 1/4

• 1/8

• 1/16

For a second-order reaction, if the initial concentration is doubled, how does the half-life change?

• Halves

• Doubles

• Remains constant

• Quadruples

The unit of rate constant for a second-order reaction is:

• L mol⁻¹ s⁻¹

• M⁻¹ s⁻¹

• (mol/L)⁻¹ s⁻¹

• All the above

For a first-order reaction with a rate constant k=0.693 min⁻¹, what is its half-life?

• 1min

• 2min

• 3min

• 4min

For a zero-order reaction with a rate constant k=0.1 mol/L/s, how long will it take for the concentration to decrease from 0.5 mol/L to 0.2 mol/L?

• 3 sec

• 5 sec

• 10 sec

• 12 sec

The overall order of a reaction is defined as:

• The sum of the stoichiometric coefficients

• The sum of the exponents in the rate law expression.

• The maximum number of molecules involved in any elementary step.

• None of these

The transition state in a reaction is characterized by:

• Maximum potential energy along the reaction coordinate.

• Minimum potential energy along the reaction coordinate

• Equal potential energy as reactants and products

• None of the above

In transition state theory, what does ΔG^‡ represent?

• Free energy of reactants

• Free energy of products

• Free energy of activated complex

• None of the above

In a reaction mechanism, if the first step is slow and the second step is fast, what can be inferred about the overall rate law?

• It depends on both steps.

• It depends only on the fast step

• It depends only on the slow step.

• It cannot be determined

According to collision theory, which of the following factors affects the rate of reaction?

• Concentration of reactants

• Temperature

• Presence of a catalyst

• All of the above