[gera19]

1) i dun understand this attached graph. Pls xplain...For example : a particular gas with TR(reduced variable-Temp)of 2.37 and PR(reduced variable-pressure) of 0.298 compared to another gas with TR=0.982 and PR=0.207. Which gas behaves more ideally(Z closest to 1)?

2) Why is the critical T greater for the partilcular gas which has higher intermolecular forces than the gas which has lower intermolecular force?

pls reply asap....tHANKS

[gera19]

Why is the critical T greater for the particular gas which has higher intermolecular forces than the other gas which has lower intermolecular forces? Can someone kindly explain??

U didnt reply exactly....

[gera19]

my teacher just replied to me. He said that :You can view liquefaction of a gas from another point of view. You can liquefy a gas by simply lowering the temperature at a given pressure. When the attractive force among gas molecules can overcome the thermal energy possessed by the gas, the attractive force will hold the molecules together into a liquid form. As the temperature is lowered, the thermal energy becomes smaller. Eventually the gas will be condensed. Therefore if the gas has a large IMF, you don't have to cool the gas to a low temperature to realize the liquefaction.

[Donaldson Tan]

the critical point of a substance is the minimum pressure and temperature whereby its fluid state cannot be distinguished from vapour or liquid state. at such state

the main difference between liquid and vapour phase is the intermolecular distance and the degree of molecular clustering. the critical state is such that the intermolecular distance and degree of molecular clustering is the boundary value where one would set to differentiate vapour and liquid state.

In principle, this means heating a liquid to its critical point is similar to boiling a liquid. The stronger the intermolecular forces, the higher the critical temperature, as more energy is needed to overcome the intermolecular forces to attain the required intermolecular distance and degree of molecular clustering to be considered as critical state. considering the case of coolng down a gas to its criitical state, stronger intermolecular forces means a small drop in temperature will reduce intermolecular distance alot, and thus facillitating molecular clustering.

Hence, a liquid with strong intermolecular forces has high critical temperature.