Question

What is the molar mass of a gas, if 2.5 g of the gas occupies 1.12 L at STP?

• A. 32 g/mol
• B. 22.4 g/mol
• C. 44 g/mol
• D. 28 g/mol

Hint:

For gases at STP, 1 mole of any ideal gas occupies 22.4 L. Always check the volume and mass units.

Answer 1

The Correct Option is A

We use the ideal gas equation for STP conditions where: - 1 mole of any ideal gas occupies 22.4 L at STP. Now, calculate the number of moles in 1.12 L of the gas: \[ \text{Moles of gas} = \frac{\text{Volume of gas}}{\text{Molar volume at STP}} = \frac{1.12}{22.4} = 0.05 \, \text{mol} \] The molar mass \( M \) of the gas is: \[ M = \frac{\text{Mass of gas}}{\text{Moles of gas}} = \frac{2.5 \, \text{g}}{0.05 \, \text{mol}} = 50 \, \text{g/mol} \] Thus, the molar mass of the gas is 50 g/mol. However, this calculation assumes standard conditions.