Question

True or False
a. The entropy of an open system cannot decrease in a spontaneous process.
T
F
b. Given that the equilibrium constant depends on the temperature only, the composition of the equilibrium mixture in a gas reaction is insensitive to the external pressure.
T
F
c. A change in external pressure has no effect on the melting temperature of a pure substance.
T
F
d. A chemical reaction for which the standard reaction Gibbs energy Δ??? is positive is impossible.
T
F

Answer 1

Entropy change of the universe must be positive and for this entropy change of the surroundings must be greater than that of the system when it releases thermal energy.

so true The entropy of an open system cannot decrease in a spontaneous process.

For most substances, increasing the pressure when a system is in equilibrium between liquid and solid phases will increase the phase transition temperature. Water is one of a few special substances for which the pressure lowers the temperature of transition. The basic reason is that water actually expands when it goes from the liquid to solid phase. In textbooks you will find the explanation for these properties by using the Clapeyron-Clausius formula, but it is perhaps most readily explained using LeChatelier's principle

so false , A change in external pressure has no effect on the melting temperature of a pure substance

TRUE : A chemical reaction for which the standard reaction Gibbs energy Δ??? is positive is impossible.

b) FALSE

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