Which statement would be the most useful for deriving the ideal gas law?
volume is directly proportional to the number of moles.
volume is inversely proportional to the temperature.
pressure is directly proportional to the volume.
pressure is inversely proportional to the number of moles.

Option (a) is the correct answer.

Explanation:

According to ideal gas equation, PV = nRT.

where,     P = pressure

               V = volume

                n = number of moles

                R = gas constant

                T = temperature

This means the following.

Pressure is directly proportional to number of moles and temperature.

Volume is directly proportional to number of moles and temperature also.

Pressure is inversely proportional to volume and vice versa.

Thus, we can conclude that the statement volume is directly proportional to the number of moles, would be the most useful for deriving the ideal gas law.