Calculate the mass fraction of nitrogen in ammonia.

To solve this problem, we write down given: NH3
Find: w (N) -?
Solution:
Let’s write down the formula for calculating the mass fraction of an element in a substance.
w = n * Ar / Mr, where
n is the number of atoms or molecules.
Ar is the relative atomic mass of the element.
Mr is the relative molecular weight of the substance.
Let’s calculate the relative molecular weight of ammonia.
Mr (NH3) = 14 + 1 * 3 = 17
The number n for nitrogen is 1, the relative atomic mass is 14
Let’s substitute the data into the formula and make the calculation.
w = 1 * 14/17 = 0.82 or 82%
Answer: the mass fraction of nitrogen in ammonia is 82%