Question

Calculate the percentage by weight of nitrogen found in urea.

Answer 1

The percent by weight:

• It is also referred to as mass percent composition and is expressed as W/W% meaning weight by weight.
• It is defined as the ratio of the mass of a solute and the mass of the solution multiplied by$100$.

Step 1: Given data

• The total molecular weight of urea (${\mathrm{CH}}_4{\mathrm{N}}_2\mathrm{O}$) is $60$ g/mol with carbon, nitrogen, oxygen, and hydrogen contributing$12$, $28$, $16$ and $4$ g/mol respectively.

Step 2: Use the formula

• Use percent by weight formula i.e. W/W%
• Here mass of solute is the total mass of all the nitrogen present in urea and the mass of solvent equals the mass of urea.
• Mass due to nitrogen = $28$ g/mol.
• Therefore, percentage by weight of nitrogen = $\frac{28}{60}\times 100$= $46.66\%$

Thus, the percentage by weight of nitrogen found in urea (${\mathrm{CH}}_4{\mathrm{N}}_2\mathrm{O}$) is $\mathbf{46}\mathbf{.}\mathbf{66}\mathbf{\%}$.