Question

In the ideal gas model, molecules are viewed as non-interacting point masses in thermal motion. Which behavior of a real CO2 gas does the is model fail to explain? Why?

a) expanding at P=constant and increasing T

b) mixing with oxygen gas in any proportions

c) becoming solid (dry ice) below -78 degrees celsius

d) occupying the entire available volume

I know the answer is letter c, I was just curious as to why.  

Answer 1

In the ideal gas model molecules were viewed to be non-interacting with each other. They were considered point particles. Real gases show ideal behaviour at high temperature and low pressure because at high temperature they have greater later energy energy and and they are thermel they are a in constant motion and it can be assumed that they are non- interacting. But when the Temperature is decreased and pressure is increased the intermolecular forces come into play and the molecules start interacting with each other. This is due to low energy of the molecules and decreased thermal motion (due to decreased temperature and increased pressure) In the similar way when temperature of con gas is decreased the intermolecular forces start operating and it is converted into solid co(dry ice)