All of the following processes lead to an increase in entropy EXCEPT A) increasing the temperature of a gas. B) melting a solid. C) chemical reactions that increase the number of moles of gas. D) forming mixtures from pure substances. E) decreasing the volume of a gas.

D) forming mixtures from pure substances.

Explanation

Entropy is the measure of randomness or disorder of a system. If a system moves from  an ordered arrangement to a disordered arrangement, the entropy is said to decrease and vice versa.

a) Increase in temperature of a gas: As increasing the temperature , increases the kinetic energy of molecules , the molecules move faster and thus entropy increases.

b) Melting a solid : The randomness will increase as liquids move freely as compared to solids and hence entropy will also increase.

c) chemical reactions that increase the number of moles of gas: As more gaseous molecules will be formed, more will be the randomness and hence entropy increases.

d) forming mixtures from pure substances: As substances in a mixture do not react chemically and thus the molecules remain same and entropy remain same.

e) decreasing the volume of a gas: According to Boyle's law, decreasing the volume will increase the pressure and thus entropy will increase.

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