Chapter 6, Problem 23A

(a)

Interpretation Introduction

Interpretation: The number of moles of sodium dihydrogen phosphate needs to be determined.

Concept Introduction: The number of moles can be calculated from mass and molar mass as follows:

  $n=\frac{m}{M}$

Here, m is mass and M is molar mass.

Answer to Problem 23A

  $3.5\times {10}^{-5}\text{ mol}$

Explanation of Solution

  ${\text{Molar mass of NaH}}_{\text{2}}{\text{PO}}_{\text{4}}\text{=Atomic mass of Na+2×Atomic mass of H atom+Atomic mass of P+4×Atomic mass of Oxygen}$

$\begin{array}{l}=22.9\times 2+1.008+30.9+4\times 16\\ =119.98\text{ g/mol}\end{array}$

  ${\text{Number of moles of NaH}}_{{}_{\text{2}}}{\text{PO}}_{\text{4}}\text{=}\frac{\text{Given mass}}{\text{Molar mass}}$

  $=\frac{4.26\times {10}^{-3}}{119.98}$

$=3.5\times {10}^{-5}\text{ mol}$

(b)

Interpretation Introduction

Interpretation: The number of moles of copper (I) chloride needs to be determined.

Concept Introduction: The number of moles can be calculated from mass and molar mass as follows:

  $n=\frac{m}{M}$

Here, m is mass and M is molar mass.

Answer to Problem 23A

  $\text{Number of moles of CuCl=5}\text{.26 mol}$

Explanation of Solution

  $\text{Molar mass of Cu=Atomic mass of Cu+Atomic mass of Cl atom}$

$\begin{array}{l}=63.5+35.4\\ =98.9\text{ g/mol}\end{array}$

  $\text{Number of moles of CuCl=}\frac{\text{Given mass}}{\text{Molar mass}}$

  $=\frac{521}{98.9}$

$=5.26\text{ mol}$

(c)

Interpretation Introduction

Interpretation: The number of moles of iron needs to be determined.

Concept Introduction: The number of moles can be calculated from mass and molar mass as follows:

  $n=\frac{m}{M}$

Here, m is mass and M is molar mass.

Answer to Problem 23A

  $2.70\text{ mol}$

Explanation of Solution

  $\text{Number of moles of Fe=}\frac{\text{Given mass}}{\text{Atomic mass}}$

  $=\frac{151\times {10}^3}{55.8}$

$=2.70\text{ mol}$

(d)

Interpretation Introduction

Interpretation: The number of moles of strontium fluoride needs to be determined.

Concept Introduction: The number of moles can be calculated from mass and molar mass as follows:

  $n=\frac{m}{M}$

Here, m is mass and M is molar mass.

Answer to Problem 23A

  $NumberofmolesofSr{F}_2=0.082$

Explanation of Solution

  ${\text{Molar mass of SrF}}_{\text{2}}\text{=Atomic mass of Sr+2×Atomic mass of F atom}$

  $\begin{array}{l}=67.6+2\times 19\\ =105.6\text{ g/mol}\end{array}$

  ${\text{Number of moles of SrF}}_{\text{2}}\text{=}\frac{\text{Given mass}}{\text{Atomic mass}}$

  $=\frac{8.76}{105.6}$

  $=0.082\text{ mol}$

(e)

Interpretation Introduction

Interpretation: The number of moles of alumiunum needs to be determined.

Concept Introduction: The number of moles can be calculated from mass and molar mass as follows:

  $n=\frac{m}{M}$

Here, m is mass and M is molar mass.

Answer to Problem 23A

  $\text{Number of moles of Al=0}\text{.046 mol}$

Explanation of Solution

  $\text{Atomic mass of Al=26}\text{.9}$

  $\text{Number of moles of Al=}\frac{\text{Given mass}}{\text{Atomic mass}}$

  $=\frac{1.26\times {10}^4}{26.9}$

  $=0.046\text{ mol}$