Chapter 8.3, Problem 39PP

Interpretation Introduction

Interpretation:

The mass of KMnO4 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 39PP

${\text{403 grams KMnO}}_4$

Explanation of Solution

The chemical formula for potassium permanganate is ${\text{KMnO}}_4$

The molar mass of ${\text{KMnO}}_4$ is calculated as:

One mole of potassium atom weighs $39\cdot 10\text{ grams}$.

One mole of maganese atom $(Mn)$ weighs $54\cdot 94\text{ grams}$.

One mole of oxygen (O) atom weigh 16 grams thus, mass of $4$ moles of oxygen $=4\times 16\text{ grams = 64 grams}$

The molar mass of ${\text{KMnO}}_4$ is

$39\cdot 10\text{ grams + 54}\cdot 94\text{ grams + 64 grams = 158}\cdot 04\text{ grams}$

Hence one mole of potassium permanganate weighs $\text{158}\cdot 04\text{ grams}$

Given $2\cdot 55\text{ moles}$ of $KMn{O}_4$

Now multiplying the molar mass with the given moles, $2\cdot 55\text{ moles }\times \frac{\text{158}\cdot 04{\text{ grams KMnO}}_4}{1\text{ mole}}$

$=403{\text{ grams KMnO}}_4$

Conclusion

Moles to mass is converted by multiplying the given moles by molar mass.