Chapter 8.3, Problem 38PP

Interpretation Introduction

Interpretation:

The mass of ZnCl₂ needs to be determined.

Concept introduction:

By multiplying the molar mass of a compound by the number of moles, the given moles get converted to mass.

Answer to Problem 38PP

$\text{5}\cdot {\text{88 grams ZnCl}}_2$

Explanation of Solution

The molar mass of ${\text{ZnCl}}_2$ is calculated first

$1$ mole of zinc equals $65\cdot 38\text{ grams}$.

$1$ mole of chlorine atom equals $35\cdot 5\text{ grams}$.

Hence $C{l}_2$ weighs $35\cdot 5\times 2=70\text{ grams}$.

$\therefore$ Molecular weight of ${\text{ZnCl}}_2=65\cdot 38+70$

$135\cdot 38\text{ grams}$

Hence one mole of ${\text{ZnCl}}_2$ weighs $135\cdot 38\text{ grams}$

Given $4\cdot 35\times {10}^{-2}\text{ moles}$ of ${\text{ZnCl}}_2$

In order to convert moles to mass, multiply the given mass by the molar mass of compound.

i.e. $4\cdot 35\times {10}^{-2}\text{ moles }\times \frac{\text{135}\cdot \text{38 grams }}{1\text{ mole}}$

$=5\cdot 88\text{ grams}$

Conclusion

Multiplying the molar mass of compound with the moles gives the mass.