Chapter 10, Problem 123A

Interpretation Introduction

Interpretation:

The method for the determination of the molar mass of a compound should be explained.

Concept introduction:

A formula that represents a certain combination of elements present in a molecule is known as a molecular formula. In a molecular formula, the simpler number of every atom is present in a molecule.

Explanation of Solution

On the basis of molecular formula, first, identify the types of atom and number of atoms present in the compound. The number of atoms present in the compound or molecule represents by subscript.

To find the molar mass of the compound, multiply the molecular weight of the atom by the corresponding subscript number.

For example:

To calculate the molar mass of ${\text{K}}_{\text{2}}{\text{CrO}}_{\text{4}}$ ,

Molar mass of potassium = 39.083 g/mole

Molar mass of chromium = 51.9961 g/mole

Molar mass of oxygen = 15.999 g/mole

Number of atoms of potassium = 2

Number of atoms of chromium = 1

Number of atoms of oxygen = 4

The molar mass of ${\text{K}}_{\text{2}}{\text{CrO}}_{\text{4}}$ = $\text{2}\left(39.083\text{ g/mole}\right)+51.9961\text{ g/mole +4}\left(15.999\text{ g/mole}\right)$

= $194.1581\text{ g/mole}$

Thus, the value of molar mass is calculated by the molecular formula of ${\text{K}}_{\text{2}}{\text{CrO}}_{\text{4}}$.