Chapter 13, Problem 68E

(a)

Interpretation Introduction

Interpretation: The initial molarity of MCHM in the river.

Concept introduction: Molarity is used as concentration unit and defined as the ratio of number of moles of solute to the volume of the solution in liter. The unit of molarity is $\text{mol/L}$

$\text{M}=\frac{\text{Number}\text{of}\text{mole}\text{of}\text{MCHM}}{\text{Volume}\text{of}\text{the}\text{solution}}$

(b)

Interpretation Introduction

Interpretation: The required volume of water to make the solution of $1.00\times {10}^{-10}\text{M}$ .

Concept introduction: Volume of the river is calculated by the formula,

   $\text{V}=\text{Lentgh}\times \text{Width}\times \text{Depth}$

By putting this value of volume in the formula of molarity, we get,

  $\text{M}=\frac{\text{Number}\text{of}\text{mole}\text{of}\text{MCHM}}{\text{Length}\times \text{Width}\times \text{Depth}}$

Now, from this formula we can calculate the depth of the river,

  $\text{Depth}=\frac{\text{Number}\text{of}\text{mole}\text{of}\text{MCHM}}{\text{Length}\times \text{Width}\times \text{M}}$