Question

Predict whether the entropy change for this process is positive or negative and explain your answer. Then, predict whether the free energy change for the process is positive or negative and explain your answer.

Answer 1

The given question is incomplete. The complete question is:

Consider the spontaneous dissolution of NaCl in water: NaCl(s) → Na+(aq) + Cl −(aq) Predict whether the entropy change for this process is positive or negative and explain your answer. Then, predict whether the free energy change for the process is positive or negative and explain your answer.

Answer: The entropy change is positive. The free energy change for the process is negative and reaction is spontaneous.

Explanation:

Entropy is defined as the degree of randomness of a system. For a system in which randomness increses , the enetropy is said to increase and $\Delta S$ is positive.

As in the given reaction : $NaCl(s)\rightarrow Na^+(aq)+Cl^-(aq)$ , the solid is dissociating to give ions , randomness increases and thus entropy is positive.

Also the dissociation of a molecule requires energy , thus the enthalpy $\Delta H$ is also positive as heat is absorbed by the system.

$\Delta G=\Delta H-T\Delta S$

$\Delta G=(+ve)-T(+ve)$

$\Delta G=-ve$ when Temperature is high.