Answer
Mass percentage of N = 35%
Mass percentage of H = 5.05%
Mass percentage of O = 60%
Work Step by Step
Strategy: To calculate the mass percentage of elements in the compound : 1- calculate the Molar mass of the compound 2- Calculate the mass of each element to the Molar mass and express this in percentage.
To find the mass percentage of N, H, and O in $NH_{4}NO_{3}$, first find the Molar mass of $NH_{4}NO_{3}$.
Molar mass of $NH_{4}NO_{3}$ = 2 x 14.0 + 4 x 1.01 + 3 x 16.0
Molar mass of $NH_{4}NO_{3}$ = 80.0 g/mol ( to three significant figures)
Based on the chemical formula $NH_{4}NO_{3}$, in 1 mole of ammonium nitrate, there are 2 moles of N, 4 moles of H, and 3 moles of O.
Mass percentage of N = $\frac{mass_(2 N moles)}{Molar mass_(NH_{4}NO_{3}) }$
Mass percentage of N = $\frac{2 \times 14.01 g}{80.0 g }$ $\times$ 100%
Mass percentage of N = 35%
Mass percentage of H = $\frac{mass_(4 H moles)}{Molar mass_(NH_{4}NO_{3}) }$
Mass percentage of H = $\frac{4 \times 1.01 g}{80.0 g }$ $\times$ 100%
Mass percentage of H = 5.05%
Mass percentage of O = $\frac{mass_(3 O moles)}{Molar mass_(NH_{4}NO_{3}) }$
Mass percentage of )O= $\frac{3 \times 16.0 g}{80.0 g }$ $\times$ 100%
Mass percentage of O = 60%
