Question

The percentage of nitrogen in urea is about:

A) 38.4

B) 46.6

C) 59.1

D) 61.3

Answer 1

Hint: To solve this problem, you need to know the molecular formula of urea. Also, you need to know the atomic masses of other substances present in the urea. By dividing the mass of nitrogen present in the urea with the total mass of the urea and multiplying with hundred, you will get the answer.

Complete step by step answer:

We know that urea plays an important role in the metabolism of living organisms and also urea is the main nitrogen-containing substance in the urine of mammals. Urea is basically an amide having two amine groups joined by the carbonyl functional group. The molecular formula of urea is

 $\text{CO(N}{\text{H}}_{\text{2}}{\text{)}}_{\text{2}}$ . Now let us calculate the percentage of nitrogen in urea:

Molecular mass of urea can be calculated as:  $(12\times 1)+(16\times 1)+(14\times 2)+(1\times 4)=60$ 

We know that the total mass of nitrogen is 28. So, by using the formula for the percentage:

 ${\displaystyle \frac{28}{60}}\times 100=46.6\mathrm{\%}$ .

So, the percentage of nitrogen present in the urea is 46.6%. Therefore, the correct option is (B).

Additional Information:

Urea has another name called carbamide. Urea is an odourless, colourless solid which is highly soluble in water and a non-toxic substance.

Note: You should know the fact that urea is the first organic substance formed in the laboratory by the scientist Wohler in 1828 which is a milestone in chemistry. Before that, it is believed that organic molecules cannot be prepared in the laboratory.