At STP, 1 mole of an ideal gas occupies 22.4 L. What volume (in L, to the nearest integer) does 2 moles occupy at STP?

Solution

Physics sir · 3 steps

Same temperature and pressure, so volume just scales with moles: double the gas, double the volume.

1. Volume scales with moles. From PV = nRT, when P and T are fixed, V is directly proportional to n. This is Avogadro's law.

   V₂/V₁ = n₂/n₁ ⇒ V₂ = 22.4 L × 2/1

2. Put in numbers. V₂ = 2 × 22.4 = 44.8 L.
3. So. 44.8 L rounds to the nearest integer as 45.

The common slip: 44. Rounding 22.4 down to 22 before doubling gives 44, not 45. Multiply first and round only at the end.

The idea to keep. At fixed temperature and pressure, every mole of any ideal gas takes up the same volume. Scale the molar volume by the number of moles.

Answer from the NTA final answer key. Solution by PrepWiser.