Which value represents the molar volume of a gas at STP?

Which value represents the molar volume of a gas at STP?

• A. 11.2 L
• B. 44.8 L
• C. 22.4 L
• D. 30.0 L

Answer: (C)

At STP, one mole of an ideal gas occupies about 22.4 liters. This comes from PV = nRT with P = 1 atm, T = 273.15 K, n = 1 mol, and R ≈ 0.0821 L·atm/(mol·K). Solving V = nRT/P gives V ≈ (1)(0.0821)(273.15)/1 ≈ 22.4 L. The other numbers would correspond to different amounts of gas (half a mole gives 11.2 L, two moles give 44.8 L), so 22.4 L is the correct molar volume at STP.

At STP, one mole of an ideal gas occupies about 22.4 liters. This comes from PV = nRT with P = 1 atm, T = 273.15 K, n = 1 mol, and R ≈ 0.0821 L·atm/(mol·K). Solving V = nRT/P gives V ≈ (1)(0.0821)(273.15)/1 ≈ 22.4 L. The other numbers would correspond to different amounts of gas (half a mole gives 11.2 L, two moles give 44.8 L), so 22.4 L is the correct molar volume at STP.