Question

Define entropy. What are the conditions for spontaneous and nonspontaneous reactions in terms of free energy change?

Answer 1

Hint There is a relationship between enthalpy, entropy and free energy of a system and it is as follows.
$G=H-TS$
Here G = free energy of the system
H = enthalpy of the system
T = Temperature of the system
S = entropy of the system

Complete step by step answer:
- In the question it is asked to define entropy and conditions favorable for spontaneous and nonspontaneous reactions in terms of free energy change.
- Entropy is a measure of the amount of order which is present in a particular system.
- By using entropy we can measure the thermal energy of the system.
- The reactions which occur without the need of external energy are called spontaneous reactions.
- The free energy is going to be released for spontaneous reactions.
- The change in free energy ($\Delta G$ ) for spontaneous reactions is negative.
- Coming to nonspontaneous reactions, the change in free energy for nonspontaneous reactions is positive because nonspontaneous reactions take energy to occur.

- Therefore the change in free energy ($\Delta G$) is negative for spontaneous reactions and change in free energy ($\Delta G$) is positive for nonspontaneous reactions.

Note: We can write the change in free energy in the following way also.
$\Delta G=\Delta H-T\Delta S$
Here $\Delta G$ = change in free energy of the system
$\Delta H$ = change in enthalpy of the system
T = Temperature of the system
$\Delta S$ = change in entropy of the system