A $$100 \text{ mL}$$ solution of $$CH_3CH_2MgBr$$ on treatment with methanol produces $$2.24 \text{ mL}$$ of a gas at STP. The weight of gas produced is ______ mg (nearest integer).

A 100 mL solution of $$CH_3CH_2MgBr$$ on treatment with methanol produces 2.24 mL of a gas at STP. We need to find the weight of the gas produced.

When a Grignard reagent reacts with methanol (an active hydrogen compound), it produces an alkane:

$$CH_3CH_2MgBr + CH_3OH \rightarrow CH_3CH_3 + Mg(OCH_3)Br$$

The gas produced is ethane ($$C_2H_6$$).

At STP, 1 mole of any gas occupies 22400 mL.

Volume of gas = 2.24 mL

$$n = \frac{2.24}{22400} = \frac{2.24}{22400} = 1 \times 10^{-4} \text{ mol}$$

Molar mass of ethane ($$C_2H_6$$) = $$2 \times 12 + 6 \times 1 = 30 \text{ g/mol}$$

$$\text{Weight} = n \times M = 1 \times 10^{-4} \times 30 = 3 \times 10^{-3} \text{ g} = 3 \text{ mg}$$

Therefore, the weight of gas produced is $$\boxed{3}$$ mg.