Chapter 6, Problem 5STP

Interpretation Introduction

Interpretation: The molar mass of calcium nitrate needs to be determined.

Concept introduction: The molar mass of a compound is calculated by taking sum of atomic masses of all the atoms of elements present in the compound.

Answer to Problem 5STP

Correct Answer: Option C. 164.1 g/mol.

Explanation of Solution

The formula of given compound is $\text{Ca}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}$ .

From the above formula, it can be seen that there is 1 Ca atom, 2 N atoms and 6 O atoms in calcium nitrate molecule.

Here, the atomic mass of Ca is 40.078 amu, N is 14.0067 amu and O is 15.999 amu.

Thus, the molar mass of calcium nitrate will be:

  $\begin{array}{l}M=40.078+\left(2\right)\left(14.0067\right)+\left(6\right)\left(15.999\right)\\ =40.078+28.0134+95.994\\ =164.0854\text{ g/mol}\\ \approx \text{164}\text{.1 g/mol}\end{array}$

Conclusion

Therefore, option C that is 164.1 g/mol is correct option.