Question

Calculate the formula mass of Potassium nitrate $\left({\mathrm{KNO}}_3\right)$.

Given: Atomic masses of K = 39u, N = 14u, 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, N = 14u, O = 16u

Step 2: Finding the formula mass for the given data

The formula mass of $\left({\mathrm{KNO}}_3\right)$ = (Number of potassium atoms x atomic mass of potassium) + (Number of nitrogen atoms x atomic mass of nitrogen) + (Number of oxygen atoms x atomic mass of oxygen)

The formula mass of $\left({\mathrm{KNO}}_3\right)$ = $\left(1\times 39\right)+\left(1\times 14\right)+\left(3\times 16\right)$

The formula mass of $\left({\mathrm{KNO}}_3\right)$ = $39+14+48=101$g/mol

Hence, the formula mass of Potassium nitrate $\left({\mathrm{KNO}}_3\right)$ is $101$g/mol