Question

An oxide of nitrogen contain 30.4% nitrogen what is the mole ratio?

Answer 1

Answer: N : O = 1: 2

Explanation:

If percentage are given then we are taking total mass is 100 grams.

So, the mass of each element is equal to the percentage given.

Mass of N = 30.4 g

Mass of O = (100-30.4) g = 69.6 g

Step 1 : convert given masses into moles.

Moles of N=$\frac{\text{ given mass of N}}{\text{ molar mass of N}}= \frac{30.4g}{14g/mole}=2.17moles$

Moles of O =$\frac{\text{ given mass of O}}{\text{ molar mass of O}}= \frac{69.6g}{16g/mole}=4.35moles$

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For N = $\frac{2.17}{2.17}=1$

For O =$\frac{4.35}{2.17}=2$

The mole ratio of N : O = 1: 2

The empirical formula will be $NO_2$

Hence the mole ratio of N : O = 1: 2