To use PV=nRT to solve for a missing variable, which quantities must be known?

To use PV=nRT to solve for a missing variable, which quantities must be known?

• A. P, V, n, and T
• B. P and V only
• C. n, R, and T
• D. V, T, and n

Answer: (A)

PV = nRT links pressure, volume, amount of substance, and temperature with the gas constant. To find any missing variable, you rearrange the equation to isolate that variable, which always requires knowing the other four pieces (the variable you’re solving for plus R is treated as the known constant). Since R is a universal constant that is typically given, the quantities you must know are pressure, volume, amount of gas, and temperature. For example, solving for temperature gives T = PV/(nR); solving for pressure gives P = nRT/V; solving for volume gives V = nRT/P; solving for the amount of gas gives n = PV/(RT).

PV = nRT links pressure, volume, amount of substance, and temperature with the gas constant. To find any missing variable, you rearrange the equation to isolate that variable, which always requires knowing the other four pieces (the variable you’re solving for plus R is treated as the known constant). Since R is a universal constant that is typically given, the quantities you must know are pressure, volume, amount of gas, and temperature. For example, solving for temperature gives T = PV/(nR); solving for pressure gives P = nRT/V; solving for volume gives V = nRT/P; solving for the amount of gas gives n = PV/(RT).