Chapter 10.1, Problem 5PP

(a)

Interpretation Introduction

Interpretation:

The number of moles present in $\text{5}\text{.75}\times {\text{10}}^{24}$ atoms of Al needs to be calculated.

Concept introduction:

In 1 mol of any substance, there are $6.022\times {10}^{23}$ units of that substance. These units can be atoms and molecules. The number of units in 1 mol of any substance is known as Avogadro’s number. It is denoted by symbol N_A.

Answer to Problem 5PP

$9.55\text{ mol of Al}$

Explanation of Solution

Given Information: The number of Al atoms is $\text{5}\text{.75}\times {\text{10}}^{24}$.

Calculation:

The number of moles can be calculated from given number of atoms as follows:

$n=\frac{N}{N_A}$

Here, $N_A$ is Avogadro’s number which is $6.022\times {10}^{23}$.

Putting the values,

$n=\frac{\text{5}\text{.75}\times {\text{10}}^{24}}{6.022\times {10}^{23}}=9.55\text{ mol}$

Thus, the number of moles of Al is 9.55 mol.

(b)

Interpretation Introduction

Interpretation:

The number of moles present in $\text{2}\text{.50}\times {\text{10}}^{20}$ atoms of Fe needs to be calculated.

Concept introduction:

In 1 mol of any substance, there are $6.022\times {10}^{23}$ units of that substance. These units can be atoms and molecules. The number of units in 1 mol of any substance is known as Avogadro’s number. It is denoted by symbol N_A.

Answer to Problem 5PP

$4.15\times {10}^{-4}\text{ mol}$ of Fe.

Explanation of Solution

Given Information: The number of Fe atom is $\text{2}\text{.50}\times {\text{10}}^{20}$.

Calculation:

The number of moles can be calculated from given number of atoms as follows:

$n=\frac{N}{N_A}$

Here, $N_A$ is Avogadro’s number which is $6.022\times {10}^{23}$.

Putting the values,

$n=\frac{\text{2}\text{.50}\times {\text{10}}^{20}}{6.022\times {10}^{23}}=4.15\times {10}^{-4}\text{ mol}$

Thus, the number of moles of Fe is $4.15\times {10}^{-4}\text{ mol}$.