Question

Calculate the formula mass of Potassium carbonate $\left({\mathrm{K}}_2{\mathrm{CO}}_3\right)$.

Given: Atomic masses of K = 39u, C = 12u, 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, C = 12u, 0 = 16u

Step 2: Finding the formula mass for the given data

Formula mass of $\left({\mathrm{K}}_2{\mathrm{CO}}_3\right)$ = (Number of potassium atoms x atomic mass of potassium) + (Number of carbon atoms x atomic mass of carbon) + (Number of oxygen atoms x atomic mass of oxygen)

Formula mass of $\left({\mathrm{K}}_2{\mathrm{CO}}_3\right)$ = $\left(2\times 39\right)+\left(1\times 12\right)+\left(3\times 16\right)$

Formula mass of $\left({\mathrm{K}}_2{\mathrm{CO}}_3\right)$ = $78+12+48=138$g/mol

Hence, the formula mass of Potassium carbonate $\left({\mathrm{K}}_2{\mathrm{CO}}_3\right)$ is $138$g/mol