Grignard reagent $\mathrm{RMgBr}(\mathrm{P})$ reacts with water and forms a gas ( Q ). One gram of Q occupies $1.4 \mathrm{dm}^{3}$ at STP. (P) on reaction with dry ice in dry ether followed by $\mathrm{H}_{3} \mathrm{O}^{+}$ forms a compound (Z). 0.1 mole of (Z) will weigh _____ g. (Nearest integer)

JEE Main · 2026 · 24 Jan 2026 · Shift 2 · Haloalkanes and Haloarenes

Grignard reagent

RMgBr (P)

reacts with water and forms a gas ( Q ). One gram of Q occupies

1.4 dm^{3}

at STP. (P) on reaction with dry ice in dry ether followed by

H_{3} O^{+}

forms a compound (Z). 0.1 mole of (Z) will weigh _____ g. (Nearest integer)

Answer: 6

At STP one gram of gas Q occupies

1.4 dm^{3}

, so its molar mass is

\frac{22.4}{1.4} = 16 g mol^{- 1}

, identifying Q as methane. Since a Grignard reagent gives the alkane on reaction with water,

R M g B r + H_{2} O \to R H + M g (O H) B r

, the reagent P is

C H_{3} M g B r

. Reaction of

C H_{3} M g B r

with dry ice followed by acidification,

C H_{3} M g B r C O_{2} H_{3} O^{+} C H_{3} C O O H

, gives acetic acid as Z (molar mass

60

). The mass of

0.1

mol of Z is

0.1 \times 60 = 6 g

JEE Main · 2026 · 24 Jan 2026 · Shift 2 · Integer answer