Question

Which one of the following statements is true? The internal energy of a system will not chage if there is no heat exchange between the system and its surroundings. The enthalpy of a reaction is always negative if more bonds are broken than formed in the reaction. The entropy of the Universe is always constant. The entropy of the universe is always increased in a spontaneous process. For a spontaneous process the enthalpy is always negative.

Answer 1

Answer:

The statement d) is true: The entropy of the universe is always increased in a spontaneous process.

Explanation:

a), b), c) and e) are false.

a) When no heat exchange occurs between the system and its surroundings , this process is called an adiabatic process. Because the system does work on the surroundings, w is a negative  quantity and there is a decrease in the system’s internal energy (since it cannot exchange heat, it will have to use its internal energy to do work).

b) Breaking a bond will always require energy, whereas forming a bond releases energy. Therefore, if more bonds are broken than formed, the enthalpy of a reaction will be positive.

c) The second law of thermodynamics states that the entropy of the universe increases in a spon taneous  process and remains unchanged in an equilibrium process. Therefore, the entropy of the universe is not always constant.

d) True.

e) According to the Gibbs equation, if ΔH is negative and ΔS is negative, then ΔG will be negative only when TΔS  is smaller in magnitude than ΔH. This condition is met when T is small.