Question

If $300\,mL$ of a gas weighs $0.368\, g$ at $STP$. What is its molecular weight?

• A. 30.16 g
• B. 2.55 g
• C. 27.5 g
• D. 37.5 g

Answer 1

Answer: (C)

27.5 g

Answer 2

At STP, $\because$ Weight of $300\, mL$ of gas
$=0.368\, g$
$\therefore$ Weight of $22400\, mL$ of gas
$=\frac{0.368 \times 2240}{300} g / mol$
$=27.47\, g / mol$
$=27.5\, g / mol$
$\because$ Molecular weight of the gas is $27.5\,g$
$[\because 22400\, mL$ of a gas contains amount equal to molecular weight of the gas.]