Chapter 10, Problem 109A

Perform the following conversions.

a. 3.50 mol of LitogofLi

b. 7.65 g of Co to mol of Co

c. 5.62 gofKrto mol ofKr

d. 0.0550 mol of As to g of As

Interpretation Introduction

(a)

Interpretation:

3.50 moles of Li should be converted to g of Li.

Concept introduction:

Number of moles of a compound is defined as the ratio of given mass of the compound to the molar or molecular mass of the compound.

The mathematical expression is given by:

Number of moles = $\frac{\text{mass of the compound}}{\text{molar mass of the compound}}$

The one mole of any substance is equal to the Avogadro number i.e. $6.022\times {10}^{23}$ atoms.

Answer to Problem 109A

Mass of 3.50 moles of Li = 24.3 g.

Explanation of Solution

The mathematical expression for the calculation of number of moles is given by:

Number of moles = $\frac{\text{mass of the compound}}{\text{molar mass of the compound}}$

The above expression is rearranged as:

$\text{Mass = Number of moles×molar mass}$

Molar mass of Lithium = 6.941 g/mole

Number of moles of lithium = 3.50 mole

Put the values,

$\text{Mass = Number of moles×molar mass of the compound}$

$\begin{array}{l}\text{Mass of lithium = 3}\text{.50 mole ×6}\text{.941 g/mole}\\ \text{ = 24}\text{.3 g}\end{array}$

Interpretation Introduction

(b)

Interpretation:

7.65 g of $\text{Co}$ should be converted to number of moles of $\text{Co}$.

Concept introduction:

Number of moles of a compound is defined as the ratio of given mass of the compound to the molar or molecular mass of the compound.

The mathematical expression is given by:

Number of moles = $\frac{\text{mass of the compound}}{\text{molar mass of the compound}}$

The one mole of any substance is equal to the Avogadro number i.e. $6.022\times {10}^{23}$ atoms.

Answer to Problem 109A

Number of moles of cobalt = $\text{0}\text{.129 mole}$

Explanation of Solution

The mathematical expression for the calculation of number of moles is given by:

Number of moles = $\frac{\text{mass of the compound}}{\text{molar mass of the compound}}$

Molar mass of cobalt = 58.9 g/mole

Mass of cobalt = 7.65 g

Put the values,

Number of moles of cobalt = $\frac{\text{7}\text{.65 g}}{\text{58}\text{.9 g/mole}}$

Number of moles of cobalt = $\text{0}\text{.129 mole}$

Interpretation Introduction

(c)

Interpretation:

5.62 g of $\text{Kr}$ should be converted to number of moles of $\text{Kr}$.

Concept introduction:

Number of moles of a compound is defined as the ratio of given mass of the compound to the molar or molecular mass of the compound.

The mathematical expression is given by:

Number of moles = $\frac{\text{mass of the compound}}{\text{molar mass of the compound}}$

The one mole of any substance is equal to the Avogadro number i.e. $6.022\times {10}^{23}$ atoms.

Answer to Problem 109A

Number of moles of krypton = $\text{0}\text{.0670 mole}$

Explanation of Solution

The mathematical expression for the calculation of number of moles is given by:

Number of moles = $\frac{\text{mass of the compound}}{\text{molar mass of the compound}}$

Molar mass of krypton = 83.8 g/mole

Mass of krypton = 5.62 g

Put the values,

Number of moles of krypton = $\frac{\text{5}\text{.62 g}}{\text{83}\text{.8 g/mole}}$

Number of moles of krypton = $\text{0}\text{.0670 mole}$

Interpretation Introduction

(d)

Interpretation:

0.0550 mole of $\text{As}$ should be converted to mass of $\text{As}$ in g.

Concept introduction:

Number of moles of a compound is defined as the ratio of given mass of the compound to the molar or molecular mass of the compound.

The mathematical expression is given by:

Number of moles = $\frac{\text{mass of the compound}}{\text{molar mass of the compound}}$

The one mole of any substance is equal to the Avogadro number i.e. $6.022\times {10}^{23}$ atoms.

Answer to Problem 109A

Mass of 0.0550 mole of $\text{As}$ = $\text{4}\text{.12 g}$.

Explanation of Solution

The mathematical expression for the calculation of number of moles is given by:

Number of moles = $\frac{\text{mass of the compound}}{\text{molar mass of the compound}}$

The above expression is rearranged as:

$\text{Mass = Number of moles×molar mass}$

Molar mass of arsenic = 74.92 g/mole

Number of moles of arsenic = 0.0550 mole

Put the values,

$\text{Mass = Number of moles×molar mass of the compound}$

$\begin{array}{l}\text{Mass of arsenic = 0}\text{.0550 mole ×74}\text{.92 g/mole}\\ \text{ = 4}\text{.12 g}\end{array}$