Chapter U4, Problem 9STP

Interpretation Introduction

Interpretation:

The number of moles present in $\text{50}\text{.0 g}$ sample of ${\text{Ca(NO}}_{\text{3}}{)}_2$ needs to be determined.

Concept introduction:

The mathematical relationship between number of moles, mass of substance and molar mass is:

$\text{number of moles = }\frac{\text{mass of the substance}}{\text{Molar mass of the substance}}$ - (1)

Answer to Problem 9STP

The number of moles present in $\text{50}\text{.0 g}$ sample of ${\text{Ca(NO}}_{\text{3}}{)}_2$ is $\text{0}\text{.305 mol}$.

Explanation of Solution

The given sample is ${\text{Ca(NO}}_{\text{3}}{)}_2$.

The molar mass of ${\text{Ca(NO}}_{\text{3}}{)}_2$ is $\text{164}\text{.088 g/mol}$.

Now, the number of moles present in $\text{50}\text{.0 g}$ of ${\text{Ca(NO}}_{\text{3}}{)}_2$ is calculated using formula:

$\text{number of moles = }\frac{\text{mass of the substance}}{\text{Molar mass of the substance}}$

Substituting the values:

$\begin{array}{l}\text{number of moles = }\frac{\text{50}\text{.0 g}}{\text{164}\text{.088 g/mol}}\\ \text{number of moles = 0}\text{.3047 mol }\simeq \text{0}\text{.305 mol}\\ \text{number of moles = 0}\text{.305 mol}\end{array}$

Since, the number ofmoles present in $\text{50}\text{.0 g}$ sample of ${\text{Ca(NO}}_{\text{3}}{)}_2$ is $\text{0}\text{.305 mol}$ so, the correct option is (a).