Chapter 10, Problem 125A

Interpretation Introduction

Interpretation:

The reason should be determined for using molar mass as a conversion factor.

Concept introduction:

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

Molar mass is defined as the ratio of mass to the number of moles. The unit of molar mass is g/mole.

Explanation of Solution

The number of moles of a compound is defined as the ratio of the given mass of the compound to the molar or molecular mass of the compound.

The mathematical expression is given by:

Number of moles = $\frac{\text{given mass of the compound}}{\text{molar mass of the compound}}$

Molar mass is used as a conversion factor that can convert between grams and moles and, moles to grams that are mass to mole ratio and, mole to mass ratio.

For atoms, the molar mass is equal to atomic weight multiplied by a molar mass constant that is 1 g/mole.

For a molecule or compound, the molar mass of the compound is equal to the sum of atomic weights of atoms/ elements present in the molecule multiplied by a molar mass constant that is 1 g/mole.

The molar mass of the compound is equal to the sum of atomic masses of all atoms present in the compound in gram/mole.

Molar mass is used as a conversion factor because the multiplication of molar mass constant that is 1 g/mole ensures that the calculation comes out to be dimensionally correct as atomic weights are dimensionless quantity.

The mathematical expression is:

$\text{molar mass (g/mole) =}\frac{\text{mass (g)}}{\text{number of moles (mole)}}$