Question

The density of a gas at STP is 2.5 $g/L$. The weight of 6.02 x 10${}^{23}$ molecules of the gas is:

• A. 28 $g$
• B. 14 $g$
• C. 42 $g$
• D. 56 $g$

Answer 1

The correct option is D 56 $g$

Density of the gas at STP = 2.5 g/L

At STP volume of the gas = 22.4 litres/mole

$6.023\times {10}^{23}$ molecules contains 1 mole of gas = Molar mass of gas

So, $Density=\frac{Mass}{Volume}⟹2.5=\frac{Molarmass}{22.4g/mol}$

$\therefore$ Molar mass = 56 g/mole