Chapter 12.5, Problem 12.9P

(a)

Interpretation Introduction

Interpretation:

The half-life period (in hours) of the given reaction has to be calculated.

Concept introduction:

Half-life of a first order reaction:

It is the time required for the reactant (substrate) concentration reduces to one-half of its initial concentration.

$\begin{array}{l}{\text{t}}_{\text{1/2}}\text{=}\frac{\text{0}\text{.693}}{\text{k}}\\ \text{where,}\\ {\text{t}}_{\text{1/2}}\text{-}\text{half-life}\text{time}\\ \text{k}\text{-}\text{rate}\text{constant}\end{array}$

(b)

Interpretation Introduction

Interpretation:

The molarity of ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$ after four half-lives has to be calculated.

Concept introduction:

Half-life of a first order reaction:

It is the time required for the reactant (substrate) concentration reduces to one-half of its initial concentration.

$\begin{array}{l}{\text{t}}_{\text{1/2}}\text{=}\frac{\text{0}\text{.693}}{\text{k}}\\ \text{where,}\\ {\text{t}}_{\text{1/2}}\text{-}\text{half-life}\text{time}\\ \text{k}\text{-}\text{rate}\text{constant}\end{array}$

(c)

Interpretation Introduction

Interpretation:

The time required to the concentration drop to $\text{25}\text{\%}$ of its initial concentration has to be calculated.

Concept introduction:

Half-life of a first order reaction:

It is the time required for the reactant (substrate) concentration reduces to one-half of its initial concentration.

$\begin{array}{l}{\text{t}}_{\text{1/2}}\text{=}\frac{\text{0}\text{.693}}{\text{k}}\\ \text{where,}\\ {\text{t}}_{\text{1/2}}\text{-}\text{half-life}\text{time}\\ \text{k}\text{-}\text{rate}\text{constant}\end{array}$