Which equation represents the ideal gas law?

• A. PV = nRT
• B. P = nRT / V
• C. PV = RT / n
• D. P = VnRT

Answer: (C)

The idea is that the ideal gas law links pressure, volume, temperature, and amount of gas through a single relationship: PV = nRT. This equation shows that for a given amount of gas at a fixed temperature, pressure and volume are inversely related—the product PV stays proportional to nT.

You can also express the same relationship by solving for pressure: P = nRT / V. This makes the inverse P–V dependence explicit: doubling the volume while keeping n and T the same halves the pressure.

The form PV = RT / n would imply that the pressure-volume product scales with RT divided by n, which ignores the expected direct proportionality to the amount of gas. In other words, it misplaces the factor of n and does not match how PV responds to changing n.

The form P = VnRT would suggest pressure increases with volume, which contradicts the inverse relationship between pressure and volume in the ideal gas law (at fixed n and T). It also breaks the correct dimensional relationship between the variables.

Overall, the canonical expression PV = nRT (or its rearranged form P = nRT / V) correctly represents the ideal gas law.