Question

Ar has a boiling point of 120 K and Xe 165 K. If the Ar is heated to the same temperature as the Xe, which gas will behave most like an ideal gas?

I know that the answer is Ar.

But what I'm looking for is explanation.

Answer 1

the behaviour of the real gases is explained with the VAN DER WAALS equation of state ,

which for 'n' moles of a gas is given by

( P + a n² / V² ) ( V - n b) = n R T

where 'a' and 'b' are van der waals constants

the van der waals constant 'a' is a measure of the van der waals force of attraction between the molecules of a given gas.Higher value of "a" means greater attraction between the molecules and hence more deviation from the ideal behaviour .

the van der waals constant "a ' value for Ar is 1.355 and for Xe is 4.192 . this means more deviation for Xe from ideal behaviour than Ar.

so Ar will behave more idealy than Xe when the temperature is same for them.