Question

Calculate the formula mass of Potassium sulphate $\left({\mathrm{K}}_2{\mathrm{SO}}_4\right)$.

Given: Atomic masses of K = 39u, S = 32u, 0 = 16u

Answer 1

Step 1: Calculating the formula mass

Formula mass is equal to the sum of atomic masses of all the atoms (or ions) present in a molecule of an ionic compound.

Step 2: Given data

Atomic masses of K = 39u, S = 32u, O = 16u

Step 2: Finding the formula mass for the given data

The formula mass of $\left({\mathrm{K}}_2{\mathrm{SO}}_4\right)$ = (Number of potassium atoms x atomic mass of potassium) + (Number of sulphur atoms x atomic mass of sulphur) + (Number of oxygen atoms x atomic mass of oxygen)

The formula mass of $\left({\mathrm{K}}_2{\mathrm{SO}}_4\right)$ = $\left(2\times 39\right)+\left(1\times 32\right)+\left(4\times 16\right)$

The formula mass of $\left({\mathrm{K}}_2{\mathrm{SO}}_4\right)$ = $78+32+64=174$g/mole

Hence, the formula mass of Potassium sulphate $\left({\mathrm{K}}_2{\mathrm{SO}}_4\right)$ is $174$g/mole