# Question a6f2d

Sep 5, 2017

${\text{NH}}_{3}$ contains 82.25 % $\text{N}$ by mass.

#### Explanation:

The formula for mass percent is

color(blue)(barul|stackrel(" ")("Mass %" = "mass of component"/"total mass" × 100 %)|)

Let's assume that we have 1 molecule of ${\text{NH}}_{3}$.

Then we have 1 atom of $\text{N}$ and 3 atoms of $\text{H}$.

We can use the Periodic Table to compute the masses:

$\boldsymbol{\underline{\text{No."color(white)(m)"Atom"color(white)(m)A_text(r)color(white)(ml)"Mass}}}$
$\textcolor{w h i t e}{l l} 1 \textcolor{w h i t e}{m m m l} \text{N} \textcolor{w h i t e}{m l} 14.01 \textcolor{w h i t e}{m} 14.01$
ul(color(white)(ll)3color(white)(mmml)"H"color(white)(mlll)1.008color(white)(m)3.024#
$\textcolor{w h i t e}{m m m m m m l} \text{Total = 17.034}$

$\text{Mass % N" = 14.01/17.034 × 100 % = 82.25 %}$