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#### For a real gas the P-V curve was experimentally plotted and it had the following appearance. With respect to liquefaction. Choose the correct statement.Option: 1 at T = 500 K, P = 40 atm, the state will be liquid.Option: 2 at T = 300 K, P = 50 atm, the state will be gas.Option: 3 at T < 300 K, P > 20 atm, the state will be gas.Option: 4 at 300 K < T < 500 K, P > 50 atm, the state will be liquid.

Liquefaction of gases -

At high pressure, molecules of gas come close to each other. As a result, intermolecular attraction forces increase. When it is allowed to escape through a nozzle into a region of low pressure, the molecules move apart.

In doing so, energy is needed to overcome intermolecular attraction forces. This energy is taken from the molecules themselves. Therefore the gas is cooled.
This process is repeated many times until the gas is completely changed into the liquid state.

(a) at T = 500 K, P = 40 atm corresponds to 'a' substance - gas

(b) at T = 300 K, P = 50 atm corresponds to 'b' substance - liquid

(c) at T < 300 K, P > 20 atm corresponds to 'c' substance - liquid

(d) at T < 500 K, P > 50 atm corresponds to 'd' substance - liquid