Chapter U4.9, Problem 7E

(a)

Interpretation Introduction

Interpretation:

Whether 1 mol of beryllium is more toxic or 10 g of beryllium needs to be determined.

Concept Introduction :

The given mass of element is converted to moles and then the toxicity is compared. The formula to calculate number of moles is shown below.

  $\text{Number of moles }=\frac{\text{Given mass}}{\text{Molar mass}}$ . (1)

Answer to Problem 7E

The toxicity of $\text{10}\text{.0}\text{g}$ beryllium is more.

Explanation of Solution

The molar mass of beryllium is $\text{9}\text{.0 g/mol}$ . Substitute given mass as $\text{10}\text{.0}\text{g}$ and molar mass as $\text{9}\text{.0 g/mol}$ in equation (1).

  $\begin{array}{c}\text{Number of moles }=\frac{10.0\text{g}}{\text{9}\text{.0}\frac{\text{g}}{\text{mol}}}\\ =1.11\text{mol}\end{array}$

This value is greater than $1.0\text{mol}$ of beryllium. Hence, $\text{10}\text{.0}\text{g}$ beryllium is more toxic.

(b)

Interpretation Introduction

Interpretation:

Whether 2 mol of arsenic is more toxic or 75 g of arsenic needs to be determined.

Concept Introduction :

The given mass of element is converted to moles and then the toxicity is compared. The formula to calculate number of moles is shown below.

  $\text{Number of moles }=\frac{\text{Given mass}}{\text{Molar mass}}$ . (1)

Answer to Problem 7E

The toxicity of $2.0\text{mol}$ arsenic is more.

Explanation of Solution

The molar mass of arsenic is $\text{74}\text{.92 g/mol}$ . Substitute given mass as $\text{75}\text{.0}\text{g}$ and molar mass as $\text{74}\text{.92 g/mol}$ in equation (1).

  $\begin{array}{c}\text{Number of moles }=\frac{75.0\text{g}}{74.92\frac{\text{g}}{\text{mol}}}\\ =1.00\text{mol}\end{array}$

This value is lower than $2.0\text{mol}$ of arsenic. Hence, $2.0\text{mol}$ of arsenic is more toxic.

(c)

Interpretation Introduction

Interpretation:

Whether 2 mol of lead is more toxic or 500 g of lead needs to be determined.

Concept Introduction :

The given mass of element is converted to moles and then the toxicity is compared. The formula to calculate number of moles is shown below.

  $\text{Number of moles }=\frac{\text{Given mass}}{\text{Molar mass}}$ . (1)

Answer to Problem 7E

The toxicity of $500.0\text{g}$ lead is more.

Explanation of Solution

The molar mass of lead is $\text{207}\text{.2 g/mol}$ . Substitute given mass as $\text{500}\text{.0}\text{g}$ and molar mass as $\text{207}\text{.2 g/mol}$ in equation (1).

  $\begin{array}{c}\text{Number of moles }=\frac{500.0\text{g}}{207.2\frac{\text{g}}{\text{mol}}}\\ =2.4\text{mol}\end{array}$

This value is more than $2.0\text{mol}$ of lead. Hence, $500.0\text{g}$ of lead is more toxic.