Question

at constant n, T and V, the pressure of a real gas is (higher, lower) than an ideal gas and at high pressures Yvette relative difference is (larger, smaller) than at low pressures.

Answer 1

Real gas equation can be written as

(P + an² /V² )(V - nb ) = nRT

and ideal gas equation can be written as

PV = nRT

There is a positive sign to pressure correction because while obtaining real gas equation we consider the intermolecular force among gaseous molecules. Hence in case of real gases the measured pressure is less than that of ideal gas, because in ideal gas the intermolecular force of attraction is nelected.

Hence at constant n, T and V, the measured pressure of a real gas is lower than an ideal gas. (answer)

At high pressure

P >> an² /V²   and hence the pressure correction term (an² /V² ) can be neglected in comparison to P, however at low pressure we cannot neglect the pressure correction term (an² /V² ).

Hence at high pressure the relative difference in pressure is smaller than at low pressure. (answer).