What is the ideal gas equation as given in the material?

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

Answer: (A)

The essential idea is that gas behavior is described by a relationship where pressure times volume scales with temperature and the amount of substance. The universal form is PV = nRT, with n representing the number of moles and R the constant that makes the units work out.

If the material presents PV = RT, that is the same equation but for the special case of one mole of gas (n = 1). In other words, PV = RT is the per-mole version. When you have more or fewer moles, you use the general form PV = nRT and include n accordingly.

R is the universal gas constant and its numeric value depends on the units you’re using (for example about 0.08206 L·atm/(mol·K) or 8.314 J/(mol·K)). This is why you’ll see PV = RT written with P in atmospheres, V in liters, and T in kelvin for a 1-mole amount, giving V ≈ 22.4 L at standard conditions for one mole.

The other expressions don’t fit because they either omit the amount of gas (n), rearrange the variables incorrectly, or mix terms in a way that isn’t dimensionally consistent with the gas law. The most complete and generally applicable form is PV = nRT; the material’s PV = RT is simply that same law applied to one mole.