Question

Which of the following conditions is true if enthalpy is negative and entropy is positive?

• A. G is negative at high temperature
• B. G is negative at low temperature
• C. free energy is always negative
• D. free energy is never negative.

Answer 1

The correct option is C

free energy is always negative

1. Enthalpy($∆H$) is the measure of total heat present in the system in which the pressure is constant whereas entropy($∆S$) is the measure of randomness of a system.
2. The value of the entropy depends on the mass of the system and can be either positive or negative.
3. If the energy is added to the system, enthalpy increases, and if the energy is removed from the system, enthalpy decreases.
4. The enthalpy and entropy are related as, $∆G=∆H-T∆S$ where $∆G$ is change in free energy and T is the temperature.
5. If $∆H$ is negative and $∆S$ is positive, then $∆G$ will always be negative, this means that the change in free energy will be negative.

Hence, Option C is the correct answer.