Which of the following is the correct expression of the ideal gas law?

• A. P V^2 = n R T
• B. P − V = nRT
• C. PV^2 = nRT
• D. PV = nRT

Answer: (D)

Understanding how pressure, volume, temperature, and amount of gas relate for an ideal gas is the key idea. For an ideal gas, the product of pressure and volume is directly proportional to the amount of substance and the temperature, with a constant R bridging the units: P V = n R T. This form shows how changes in one quantity affect the others: increasing temperature or the number of moles raises P V, while increasing volume lowers P V at fixed n and T. The units also line up neatly: P V has units of energy (joules) when P is in pascals and V in cubic meters, and n R T has the same units since R converts per-mole quantities into energy units. The other expressions would either mix units inappropriately or imply relationships that don’t match how gases actually behave (for example, subtracting V from P or involving V squared). So the expression that correctly represents the ideal gas law is P V = n R T.