Chapter 10, Problem 93A

Determine the number of moles in each substance.

a. $\text{3}\text{.25 }\times {\text{ 10}}^{\text{20}}$ atoms of lead

b. $\text{4}\text{.96 }\times {\text{ 10}}^{\text{24}}$ molecules ofglucose

c. $\text{1}\text{.56 }\times {\text{ 10}}^{\text{23}}$ formula units of sodium hydroxide

d. $\text{1}\text{.25 }\times {\text{ 10}}^{\text{25}}$ copper(II) ions

Interpretation Introduction

Interpretation:

The number of moles of lead in $3.25\times {\text{ 10}}^{\text{20}}$ atoms needs to be determined.

Concept introduction:

The mole concept provides the relation between moles, mass and molar mass. The mathematical expression of mole concept can be written as:

$\text{Mole =}\frac{\text{Mass}}{\text{Molar mass}}$

1 mole of any substance contains $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ number of particles or atoms or molecules.

Answer to Problem 93A

$5.40\times 10^{-4}moles$

Explanation of Solution

Number of atoms = $3.25\times {\text{ 10}}^{\text{20}}$

1 mole = $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ atoms

Calculate moles:

$3.25\times 10^{20}atoms\times \frac{1mole}{6.022\times 10^{23}atoms}=5.40\times 10^{-4}moles$

Interpretation Introduction

Interpretation:

The number of moles of glucose in $4.96\times {\text{ 10}}^{\text{24}}$ molecules needs to be determined.

Concept introduction:

The mole concept provides the relation between moles, mass and molar mass. The mathematical expression of mole concept can be written as:

$\text{Mole =}\frac{\text{Mass}}{\text{Molar mass}}$

1 mole of any substance contains $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ number of particles or atoms or molecules.

Answer to Problem 93A

$\text{8}\text{.24 moles}$

Explanation of Solution

Number of molecules = $4.96\times {\text{ 10}}^{\text{24}}$

1 mole = $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ molecules

Calculate moles:

$\text{4}{\text{.96× 10}}^{\text{24}}\text{molecules×}\frac{\text{1 mole}}{\text{6}{\text{.022 × 10}}^{\text{23}}\text{molecules}}\text{= 8}\text{.24 moles}$

Interpretation Introduction

Interpretation:

The number of moles of sodium hydroxide in $1.56\times {\text{ 10}}^{\text{23}}$ formula units needs to be determined.

Concept introduction:

The mole concept provides the relation between moles, mass and molar mass. The mathematical expression of mole concept can be written as:

$\text{Mole =}\frac{\text{Mass}}{\text{Molar mass}}$

1 mole of any substance contains $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ number of particles or atoms or molecules.

Answer to Problem 93A

$\text{0}\text{.260 moles}$

Explanation of Solution

Number of formula units = $1.56\times {\text{ 10}}^{\text{23}}$

1 mole = $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ formula units

Calculate moles:

$1.56\times {\text{ 10}}^{\text{23}}\text{ formula units×}\frac{\text{1 mole}}{\text{6}{\text{.022 × 10}}^{\text{23}}\text{formula units}}\text{= 0}\text{.260 moles}$

Interpretation Introduction

Interpretation:

The number of moles of copper (II) ionsin $1.25\times {\text{ 10}}^{\text{25}}$ needs to be determined.

Concept introduction:

The mole concept provides the relation between moles, mass and molar mass. The mathematical expression of mole concept can be written as:

$\text{Mole =}\frac{\text{Mass}}{\text{Molar mass}}$

1 mole of any substance contains $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ number of particles or atoms or molecules.

Answer to Problem 93A

$\text{20}\text{.7 moles}$

Explanation of Solution

Number of ions = $1.25\times {\text{ 10}}^{\text{25}}$

1 mole = $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ ions

Calculate moles:

$1.25\times {\text{ 10}}^{\text{25}}\text{ ions×}\frac{\text{1 mole}}{\text{6}{\text{.022 × 10}}^{\text{23}}\text{ions}}\text{= 20}\text{.7 moles}$