Question

In diammonium phosphate, $(N{H}_4{)}_{2}HP{O}_4$, the percentage of $P_2{O}_5$ is

Answer 1

Two mole of $(N{H}_4{)}_{2}HP{O}_4$ gives one mole of $P_2{O}_5$ so
% of $P_2{O}_5=142\times 100/264=53.78$ %.
The nearest integer value is 54.