Chapter 10.4, Problem 56PP

Interpretation Introduction

Interpretation:

The percent by mass of each element in ${\text{CaCl}}_{\text{2}}$ needs to be determined.

Concept used: A compound having atoms of elements constitute it they are present in different compositions, through, stoichiometry−one can find percentage by mass of each element in the compound. The molecular formula is required for this.

$\text{Percent composition by mass = }\frac{\text{Mass of atom}}{\text{Total mass of compound}}\times 100$

Answer to Problem 56PP

Calcium $\left(Ca\right)\Rightarrow 36\cdot 03\%$

Chlorine $\left(Cl\right)\Rightarrow 63\cdot 9\%$

Explanation of Solution

Given information:

Molecular formula for Calcium chloride ${\text{CaCl}}_{\text{2}}$

To find the percent by mass of ${\text{CaCl}}_{\text{2}}$

Atomic mass of Calcium $\text{=40 g}$

Atomic mass of Chlorine $\text{=35}\cdot \text{5 g}$

$\text{Mass of atom in the compound}\Rightarrow \text{number of atoms in the compound}\times \text{atomic mass of that compound}$ Total molecular mass $\Rightarrow CaC{l}_2\Rightarrow 40+2\times 35\cdot 5\Rightarrow 111\text{ g}$

Percent by mass of chlorine $\Rightarrow \frac{2\times 35\cdot 5}{111}\times 100$

$\Rightarrow \frac{7100}{111}=63\cdot 9\%$

Percent by mass of calcium $\Rightarrow \frac{40}{111}\times 100\Rightarrow 36\cdot 03\%$.