Question

Which expression represents the percent by mass of nitrogen in NH 4 NO 3 ?

Answer 1

Answer: a) $\frac{28gN}{80gNH_4NO_ 3}\times 100\%$

Explanation: Mass percentage is defined as the ratio of the mass of the particular element to the total mass of the substance multiplied by 100.

${\text{mass percentage}=\frac{\text{mass of the element}}{\text{Total mass}}\times {100}$

mass of nitrogen[2 atoms of N] = 28 g

Total mass of $NH_4NO_ 3=2\times {\text {Mass of nitrogen}}+4\times {\text {mass of hydrogen}}+3\times {\text {mass of oxygen}}$

$=2\times 14+4\times 1 +3\times 16=80 g$

${\text{mass percentage}=\frac{28}{80}\times {100}\%$