why is force of attraction of O₂ less than CH₄ in the deviation of real gas from ideal gas graph when oxygen has molecular wt. 32 while methane has 16?

Note .. Both Oxygen and Methane are non polar and have weak van der waal forces.

Oxygen has 32 molecular wt. while methane has 16 molecular wt.. 32 molecular wt. indicates it must have more volume  but still force of attraction is more in methane than in oxygen. this is because vander waal forces depend upon surface area of molecule.. Oxygen has double bond while methane has single bond along with tetrahedral structure. so surface area of methane is more than oxygen. therefore force of attraction is more in methane than oxygen gas.