Chapter 10.3, Problem 39PP

Interpretation Introduction

Interpretation:

The chemical formula for potassium permanganate needs to be written and the mass of 2.55 mol of it needs to be determined.

Concept introduction:

The number of moles can be used to calculate mass of a substance using its molar mass. The relation is represented as follows:

$\begin{array}{l}n=\frac{m}{M}\\ Or,\\ m=n\times M\end{array}$

Here, n is number of moles, m is mass and M is molar mass.

Answer to Problem 39PP

The chemical formula of potassium permanganate is ${\text{KMnO}}_{\text{4}}$ and the mass of 2.55 mol is 403 g.

Explanation of Solution

Given Information:

The number of moles of potassium permanganate is 2.55 mol.

Calculation:

To calculate the mass, first calculate molar mass of potassium permanganate using its chemical formula.

The chemical formula of potassium permanganate is ${\text{KMnO}}_{\text{4}}$

From the above formula, there is 1 K atom, 1 Mn atom and 4 O atoms in 1 molecule of ${\text{KMnO}}_{\text{4}}$.

The molar mass of K, Mn and O is 39.1 g/mol, 54.95 g/mol and 16 g/mol respectively. Therefore, molar mass of ${\text{KMnO}}_{\text{4}}$ will be:

${\text{M}}_{{\text{KMnO}}_{\text{4}}}=39.1\text{ g/mol+}54.95\text{ g/mol+4}\left(16\text{ g/mol}\right)=158.05\text{ g/mol}$

Mass of ${\text{KMnO}}_{\text{4}}$ can be calculated as follows:

$m=n\times M$

Putting the values,

$\begin{array}{l}m=\left(\text{2}\text{.55 mol}\right)\left(158.05\text{ g/mol}\right)\\ =403\text{ g}\end{array}$

Conclusion

Therefore, mass of ${\text{KMnO}}_{\text{4}}$ is 403 g.