Question

What is the percentage of carbon in urea?

(Atomic mass C = 12, H = 1, N = 14, O = 16)

Options

• 20%

• 26.6%

• 6.67%

• 46.0%

Answer 1

20%

Explanation:

Molar mass of urea (i.e. NH₂CONH₂)

= 2 × atomic mass of N + 4 × atomic mass of H + 1 × atomic mass of O + 1 × atomic mass of C.

= 2 × 14 + 4 × 1 + 1 × 16 + 1 × 12 

= 60 g

As we know that,

Percentage or mass % of an element

`= "Mass of that element in the compound"/"Molar mass of the compound" xx 100`

∴ Percentage of C = `(1 xx 12)/60 xx 100`

= 20 %