Chapter 10, Problem 94A

Interpretation Introduction

(a)

Interpretation:

The number of moles of Si needs to be determined.

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 94A

$2.5\times {10}^{-9}\text{ moles}$

Explanation of Solution

The number of atoms of Si is $1.51\times {10}^{15}$.

In 1 mol of any compound there are $6.022\times {10}^{23}$ molecules. Thus, number of moles of Si can be calculated as follows:

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

Putting the values,

$\begin{array}{c}n=\frac{1.51\times {10}^{15}}{6.022\times {10}^{23}}\text{ mol}\\ =2.5\times {10}^{-9}\text{ moles}\end{array}$

Interpretation Introduction

(b)

Interpretation:

The number of moles of ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ needs to be converted to number of molecules.

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 94A

$2.56\times {10}^{22}\text{ molecules}$

Explanation of Solution

The given number of moles of sulphuric acid is $4.25\times {10}^{-2}\text{ mol}$.

In 1 mol of any compound there are $6.022\times {10}^{23}$ molecules. Thus, number of molecules in $4.25\times {10}^{-2}\text{ mol}$ will be:

$N=n{N}_A$

Putting the values,

$\begin{array}{c}N=\left(4.25\times {10}^{-2}\text{ mol}\right)\left(6.022\times {10}^{23}\text{ molecules/mol}\right)\\ =2.56\times {10}^{22}\text{ molecules}\end{array}$

Interpretation Introduction

(c)

Interpretation:

The number of moles of ${\text{CCl}}_{\text{4}}$ needs to be determined.

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 94A

$1.5\times {10}^2\text{ moles}$

Explanation of Solution

The given number of molecules of CCl₄ is $8.95\times {10}^{25}$.

In 1 mol of any compound there are $6.022\times {10}^{23}$ molecules. Thus, number of moles corresponding $8.95\times {10}^{25}$ molecules will be:

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

Putting the values,

$\begin{array}{c}n=\frac{8.95\times {10}^{25}}{6.022\times {10}^{23}}\text{ mol}\\ =1.5\times {10}^2\text{ moles}\end{array}$

Interpretation Introduction

(d)

Interpretation:

The number of atoms of Ca needs to be determined.

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 94A

$3.55\times {10}^{24}\text{ atoms}$

Explanation of Solution

The given number of moles of Ca is 5.90 mol.

In 1 mol of any compound there are $6.022\times {10}^{23}$ molecules. Thus, number of atoms in 5.90 mol will be:

$N=n{N}_A$

Putting the values,

$\begin{array}{c}N=\left(5.90\text{ mol}\right)\left(6.022\times {10}^{23}\text{ atoms/mol}\right)\\ =3.55\times {10}^{24}\text{ atoms}\end{array}$