In general, real gases behave most ideally at temperatures and pressures. The behavior of real gases can be described using the van der Waals equation [P + (n2a/V2)](V-nb) = nRT The values of a and b are given below for the two real gases carbon dioxide and krypton. The gas in which deviations from ideal behavior due to intermolecular forces are expected to be the smallest is . The gas that would be expected to behave least like an ideal gas at high pressures is .