Chapter 10.1, Problem 15LC

Interpretation Introduction

Interpretation: The molar mass of ${\text{CaSO}}_4$ should be calculated.

Concept Introduction: The mass in grams of one mole of the compound is said to be its molar mass.

Answer to Problem 15LC

The molar mass of ${\text{CaSO}}_4$ is $\text{136}\text{.2 g/mol}$ .

Explanation of Solution

To determine the molar mass of ${\text{CaSO}}_4$ , the sum of the masses of Ca, S and O elements are added up.

The moles of Ca, S and O are converted to grams of Ca, S and O as:

  $\begin{array}{l}\text{1 mol Ca }\times \frac{40.1\text{ g Ca}}{1\text{ mol Ca}}\text{ = 40}\text{.1 g Ca}\\ \text{1 mol S }\times \frac{32.1\text{ g S}}{1\text{ mol S}}\text{ = 32}\text{.1 g S}\\ \text{4 mol O }\times \frac{\text{16}\text{.0 g O}}{1\text{ mol O}}\text{ = 64}\text{.0 g O}\end{array}$

The mass of 1 mol of ${\text{CaSO}}_4$ is:

  $\begin{array}{l}{\text{mass of 1 mol CaSO}}_4\text{ = 40}\text{.1 g Ca + 32}\text{.1 g S + 64}\text{.0 g O}=\text{ 136}\text{.2 g}\\ {\text{molar mass of CaSO}}_4=\text{ 136}\text{.2 g/mol}\end{array}$

Hence, the molar mass of ${\text{CaSO}}_4$ is $\text{136}\text{.2 g/mol}$ .