Chapter 10, Problem 60A

(a)

Interpretation Introduction

Interpretation: The molar mass of ${\text{H}}_{\text{3}}{\text{PO}}_{\text{4}}$ needs to be calculated.

Concept Introduction: The molar mass of a substance can be calculated by taking the sum of the atomic mass of the total number of elements present in the compound.

Explanation of Solution

The given compound is ${\text{H}}_{\text{3}}{\text{PO}}_{\text{4}}$ . The elements present in the compound are H, P, and O. Atomic mass of H, P and O is 1 g/mol, 31 g/mol, and 16 g/mol respectively. Calculate the molar mass of the compound as follows:

  $\begin{array}{c}M=3\left(1\text{ g/mol}\right)+31\text{ g/mol}+4\left(16\text{ g/mol}\right)\\ =3+31+64\\ =98\text{ g/mol}\end{array}$

Therefore, the molar mass of ${\text{H}}_{\text{3}}{\text{PO}}_{\text{4}}$ is 98 g/mol.

(b)

Interpretation Introduction

Interpretation: The molar mass of ${\text{N}}_{\text{2}}{\text{O}}_{\text{3}}$ needs to be calculated.

Concept Introduction: The molar mass of a substance can be calculated by taking the sum of the atomic mass of the total number of elements present in the compound.

Explanation of Solution

The given compound is ${\text{N}}_{\text{2}}{\text{O}}_{\text{3}}$ . The number of atoms present in the compound are N and O. Atomic mass of N and O is 14 g/mol and 16 g/mol respectively.

The molar mass of the compound is calculated as follows:

  $\begin{array}{c}{\text{N}}_{\text{2}}{\text{O}}_{\text{3}}=2\left(14\text{ g/mol}\right)+3\left(16\text{ g/mol}\right)\\ =\left(28+48\right)\text{ g/mol}\\ =76\text{ g/mol}\end{array}$

Therefore, the molar mass of ${\text{N}}_{\text{2}}{\text{O}}_{\text{3}}$ is $76\text{ g/mol}$ .

(c)

Interpretation Introduction

Interpretation: The molar mass of ${\text{CaCO}}_{\text{3}}$ needs to be calculated.

Concept Introduction: The molar mass of a substance can be calculated by taking the sum of the atomic mass of the total number of elements present in the compound.

Explanation of Solution

The given compound is ${\text{CaCO}}_{\text{3}}$ . The atoms present in the compound are Ca, C and O. Atomic mass of Ca, C, and O is 40 g/mol, 12 g/mol, and 16 g/mol respectively.

Calculate the molar mass of the compound as follows:

  $\begin{array}{c}{\text{CaCO}}_{\text{3}}=40\text{ g/mol}+\text{12 g/mol}+\text{3}\left(16\text{ g/mol}\right)\\ =100\text{ g/mol}\end{array}$

Therefore, the molar mass of ${\text{CaCO}}_{\text{3}}$ is $100\text{ g/mol}$ .

(d)

Interpretation Introduction

Interpretation: The molar mass of ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{SO}}_{\text{4}}$ needs to be calculated.

Concept Introduction: The molar mass of a substance can be calculated by taking the sum of the atomic mass of the total number of elements present in the compound.

Explanation of Solution

The given compound is ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{SO}}_{\text{4}}$ . The atoms present in the compound are N, H, S, and O. Atomic mass of N, H, S, and O is 14 g/mol, 1 g/mol, 32 g/mol, and 16 g/mol respectively.

The molar mass of the compound is calculated as follows:

  $\begin{array}{c}{\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{SO}}_{\text{4}}=2\left(14\text{ g/mol}\right)+8\left(1\text{ g/mol}\right)+32\text{ g/mol+4}\left(16\text{ g/mol}\right)\\ =\left(28+8+32+64\right)\text{g/mol}\\ =132\text{ g/mol}\end{array}$

Therefore, the molar mass of ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{SO}}_{\text{4}}$ is $132\text{ g/mol}$

(e)

Interpretation Introduction

Interpretation: The molar mass of ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}{\text{O}}_{\text{2}}$ needs to be calculated.

Concept Introduction: The molar mass of a substance can be calculated by taking the sum of the atomic mass of the total number of elements present in the compound.

Explanation of Solution

The given compound is ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}{\text{O}}_{\text{2}}$ . The atoms present in the compound are C, H, and O. Atomic number of C, H, and O is 12 g/mol, 1 g/mol, and 16 g/mol respectively.

The molar mass of the compound is calculated as follows:

  $\begin{array}{c}{\text{C}}_{\text{4}}{\text{H}}_{\text{9}}{\text{O}}_{\text{2}}=4\left(12\text{ g/mol}\right)+9\left(1\text{ g/mol}\right)+2\left(16\text{ g/mol}\right)\\ =48+9+32\\ =89\text{ g/mol}\end{array}$

Therefore, the molar mass of ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}{\text{O}}_{\text{2}}$ is 89 g/mol.

(f)

Interpretation Introduction

Interpretation: The molar mass of ${\text{Br}}_2$ needs to be calculated.

Concept Introduction: The molar mass of a substance can be calculated by taking the sum of the atomic mass of the total number of elements present in the compound.

Explanation of Solution

The given compound is ${\text{Br}}_2$ . Here, the atomic mass of Br is 80 g/mol; thus, the molar mass of Br can be calculated as follows:

  $\begin{array}{c}M=2\left(80\text{ g/mol}\right)\\ =160\text{ g/mol}\end{array}$

Therefore, the molar mass of ${\text{Br}}_2$ is $160\text{ g/mol}$