Question

Determine the percentage of oxygen in ammonium nitrate.
(A) 60%
(B) 80%
(C) 70%
(D) 55%

Answer 1

Hint: Write the molecular formula for the compound ammonium nitrate. Now find the total mass of the compound and the mass of oxygen present in the compound. Now the ratio of the two values will help you to find the answer in decimal values. Now multiplying the value with 100 will give the composition of oxygen in terms of percentage and thus the answer as well.

Complete step by step answer:
We will calculate the mass of the compound ammonium nitrate. The molecular formula of ammonium nitrate is $N{{H}_{4}}N{{O}_{3}}$.
The atoms present in $N{{H}_{4}}N{{O}_{3}}$ are nitrogen, hydrogen and oxygen.
Mass of nitrogen atom = 14 g
Mass of hydrogen atom = 1 g
Mass of oxygen atom = 16 g
There are 2 atoms of nitrogen, 4 atoms of hydrogen and 3 atoms of oxygen in 1 molecule of $N{{H}_{4}}N{{O}_{3}}$.
Thus, the molecular mass = (2 $\times$ 14) + (4 $\times$ 1) + (3 $\times$ 16) = 80 g
Mass of oxygen present in the compound = (3 $\times$ 16) = 48 g
Ratio of mass of oxygen to the total mass of compound = 0.6
Thus, the percentage of oxygen in ammonium nitrate becomes (0.6 $\times$ 100) = 60%
So, the correct answer is “Option A”.

Note: It is important to know that in the above question we need to find the percentage of oxygen in the compound in terms of mass i.e. mass percentage and not in any other type of concentration. A close look at the options will indicate the above statement.