JEE Main · 2026 · 02 Apr 2026 · Shift 2 · Some Basic Concepts of Chemistry

Complete combustion of X g of an organic compound gave 0.25 g of

CO X_{2}

and 0.12 g of

H X_{2} O

. If the % of carbon is 25% and of hydrogen is 4.89%, then X = _____

\times 1 0^{- 3}

g. (Nearest integer)
(Molar mass of C, H and O are 12, 1 and 16

g mol^{- 1}

respectively.)

Answer: (A)

Solution

All the carbon of the sample emerges as

CO X_{2}

, so its mass is

\frac{0.25}{44} \times 12 = 0.0682

g. Since this carbon is

25%

of the sample,

X = \frac{0.0682}{25} \times 100 = 0.2727 g .

The hydrogen check,

\frac{0.12}{18} \times 2 = 0.0133

g amounting to

4.89%

0.2727

g, confirms the mass. Written as

X \times 1 0^{- 3}

g, the value is

273

JEE Main · 2026 · 02 Apr 2026 · Shift 2 · Single correct option