Chapter 11, Problem 75A

(a)

Interpretation Introduction

Interpretation:

The number of moles in $54.0\text{ L}$ of nitrogen dioxide (at STP) needs to be calculated.

Concept Introduction:

A mole is the amount of substance that contains $6.022\times {10}^{23}$ particles. The formula to calculate the number of moles is:

  $\text{Number of moles = }\frac{\text{Given mass}}{\text{Molar mass}}$

Answer to Problem 75A

The number of moles present in $54.0\text{ L}$ of nitrogen dioxide (at STP) is $\text{2}\text{.41 mol}$ .

Explanation of Solution

At STP, one mole of a substance occupies $\text{22}\text{.4 L}$ of volume. Now, calculate the number of moles present in $54.0\text{ L}$ of nitrogen dioxide.

In $54.0\text{ L}$ :

  $\frac{\text{1 mol}}{\text{22}\text{.4 L}}\text{× 54}\text{.0 L = 2}\text{.41 mol}$

(b)

Interpretation Introduction

Interpretation:

The number of moles in $1.68g$ magnesium ions needs to be determined.

Concept Introduction:

A mole is the amount of substance that contains $6.022\times {10}^{23}$ particles. The formula to calculate the number of moles is:

  $\text{Number of moles = }\frac{\text{Given mass}}{\text{Molar mass}}$

Answer to Problem 75A

The number of moles in $1.68g$ magnesium ions is $\text{0}\text{.069 moles}$ .

Explanation of Solution

Molar of mass of magnesium is: $24.305\frac{g}{mol}$

Now, calculate the number of moles present in $1.68g$ magnesium ions.

  $\begin{array}{l}\text{Number of moles = }\frac{\text{Given mass}}{\text{Molar mass}}\\ \text{ = }\frac{\text{1}\text{.68 g}}{\text{24}\text{.305}\frac{\text{g}}{\text{mol}}}\\ \text{ = 0}\text{.069 moles}\end{array}$

(c)

Interpretation Introduction

Interpretation:

The number of moles in $\text{69}\text{.6 g}$ sodium hypochlorite needs to be calculated.

Concept Introduction:

A mole is the amount of substance that contains $6.022\times {10}^{23}$ particles. The formula to calculate the number of moles is:

  $\text{Number of moles = }\frac{\text{Given mass}}{\text{Molar mass}}$

Answer to Problem 75A

The number of moles in $69.6\text{ g}$ sodium hypochlorite is $\text{0}\text{.934 moles}$ .

Explanation of Solution

Molar mass of sodium hypochlorite is $74.4\text{4 }\frac{\text{g}}{\text{mol}}$

  $\begin{array}{l}\text{Number of moles = }\frac{\text{Given mass}}{\text{Molar mass}}\\ \text{ = }\frac{\text{69}\text{.6 g}}{\text{74}\text{.44}\frac{\text{g}}{\text{mol}}}\\ \text{ = 0}\text{.934 moles}\end{array}$

(d)

Interpretation Introduction

Interpretation:

The number of moles in $4.27\times {10}^{24}$ molecules of carbon monoxide needs to be determined.

Concept Introduction:

A mole is the amount of substance that contains $6.022\times {10}^{23}$ particles or molecules. The formula to calculate the number of moles is:

  $\text{Number of moles = }\frac{\text{Given mass}}{\text{Molar mass}}$

Answer to Problem 75A

The number of moles in $4.27\times {10}^{24}$ molecules of carbon monoxide is $\text{7}\text{.09 moles}$ .

Explanation of Solution

Calculate the number of moles present in $4.27\times {10}^{24}$ molecules of carbon monoxide.

  $\frac{\text{1 mol}}{\text{6}{\text{.022×10}}^{\text{23}}\text{ molecules}}\text{ × 4}{\text{.27×10}}^{\text{24}}\text{ molecules = 7}\text{.09 moles}$