Grignard reagent RMgBr (P) reacts with water and forms a gas (Q). One gram of Q occupies 1.4 dm³ at STP. (P) on reaction with dry ice in dry ether followed by H₃O⁺ forms a compound (Z). 0.1 mole of (Z) will weigh ___

Grignard reagent RMgBr reacts with water and forms a gas which occupies 1.4 dm3 at STP. On reaction with dry ice it forms a compound

Q. Grignard reagent RMgBr (P) reacts with water and forms a gas (Q). One gram of Q occupies 1.4 dm³ at STP. (P) on reaction with dry ice in dry ether followed by H₃O⁺ forms a compound (Z). 0.1 mole of (Z) will weigh ____ g. (Nearest integer)

Correct Answer: 6

Explanation

Grignard reagent reacts with water to give alkane:

RMgBr + H₂O → RH + Mg(OH)Br

Thus gas (Q) is alkane RH.

At STP, 1 mole of gas occupies 22.4 dm³.

Given:

1 g of gas occupies 1.4 dm³

Molar mass of gas:

= 22.4 / 1.4 = 16 g mol⁻¹

So RH has molar mass 16, which corresponds to methane (CH₄).

Hence R = CH₃.

When RMgBr reacts with dry ice followed by acidic hydrolysis:

RMgBr + CO₂ → RCOO⁻MgBr → RCOOH

So compound (Z) is CH₃COOH (acetic acid).

Molar mass of acetic acid:

= 60 g mol⁻¹

Mass of 0.1 mole:

0.1 × 60 = 6 g

Hence, the required mass is 6 g.

Explanation

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