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Compressibility factor of a gas is given by the equation Z=PVnRT. On this basis, mark the correct statement.
A.When Z>1, real gases get compressed easily.
B.When Z=1, real gases get compressed easily.
C.When Z>1, real gases are difficult to compress.
D.When Z=1, real gases are difficult to compress.

Answer
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Hint: Deviation of real gas from ideal behaviour is expressed using compressibility factor.An ideal gas is a theoretical gas composed of many randomly moving point particles that are not subject to interparticle interactions. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics.

Complete step by step answer:
Compressibility factor of a gas is given by,
Z=PVnRT
For ideal gas, PV=nRT
Hence the value of compressibility factor Z will be equal to 1. For real gases the equation, PV=nRTcannot be true. Hence Z cannot be equal to one. Z for real gases will be less than one or greater than one.
When Z<1, the gas becomes more compressible and when Z>1, the gas becomes less compressible.
Let us look into the options given.
Option a says that when Z>1, real gases get compressed easily. This statement is wrong as we discussed. When Z>1, real gases are easy to compress. Because at this condition the molecular attraction dominates which favours compression. Hence Option a is wrong.
Option b says that when Z=1, real gases get compressed easily. For real gases Z is not equal to one. Hence this statement is wrong.
Option c says that when Z>1, real gases are difficult to compress. This statement is correct. When Z>1, the gas becomes less compressible. The reason for this is that when Z>1, the forces of attraction between the molecules is weak. The attraction should be strong for compression to happen.
Option d says that When Z=1, real gases are difficult to compress. Real gases cannot have the value of Z as one. Hence this statement is also wrong.
Hence the correct option is C.

Note:
At Z>1, PV>nRT for real gases. As pressure increases the value of PV increases and gas becomes less compressible. Repulsive forces dominate at this condition.