Chapter 16, Problem 57A

(a)

Interpretation Introduction

Interpretation: The molarity should be defined and the calculation of the same must be discussed.

Concept Introduction:

Moles are the units used to represent the smaller units like atoms and molecules and the value of mole is given as $6\cdot 02214076\times {10}^{23}$ .

The formula to calculate the molarity of the solution is given as:

  $\text{Molarity}=\frac{\text{Moles solute}}{\text{Litre solution}}$

Answer to Problem 57A

The molarity of $1.0\text{KCL}$ in $750\text{mL}$ solution is $1.33\text{M}$ .

Explanation of Solution

A solution contains $1.0\text{moles}$ of potassium chloride $\left(\text{KCL}\right)$ in $750\text{mL}$ (milli-litre).

Write the formula to calculate molarity.

  $\text{Molarity}=\frac{\text{Moles solute}}{\text{Litre solution}}$

The moles of solute is $1.0$

Litre solution is $750\text{mL}$ .

Convert $\text{mL}$ to $\text{L}$ .

  $\begin{array}{c}750\text{mL}=750\times \frac{1\text{L}}{100\text{mL}}\\ =0.75\text{L}\end{array}$

Therefore, molarity is calculated as:

  $\begin{array}{c}\text{Molarity}=\frac{1.0}{0.75}\\ =1.33\text{M}\end{array}$

(b)

Interpretation Introduction

Interpretation: The molarity should be defined and the calculation of the same must be discussed.

Concept Introduction: The molarity of a substance is defined as the number of moles of the solute present in 1 L of solution.

Moles are the units used to represent the smaller units like atoms and molecules and the value of mole is given as $6\cdot 02214076\times {10}^{23}$ .

The formula to calculate the molarity of the solution is given as:

  $\text{Molarity}=\frac{\text{Moles solute}}{\text{Litre solution}}$

Answer to Problem 57A

The molarity $0.50\text{moles}$ of magnesium chloride in $1.5\text{litre}$ solution is $0.33\text{M}$ .

Explanation of Solution

A solution contains $0.50\text{moles}$ of magnesium chloride $\left(\text{MgCl2}\right)$ in $1.5\text{litre}$ .

Write the formula to calculate molarity.

  $\text{Molarity}=\frac{\text{Moles solute}}{\text{Litre solution}}$

The moles of solute is $0.50$

Litre solution is $1.5\text{L}$ .

Therefore, molarity is calculated as:

  $\begin{array}{c}\text{Molarity}=\frac{0.50}{1.5}\\ =0.34\text{M}\end{array}$