Question

In which set of conditions would result in a spontaneous reaction?

A. An exothermic reaction; a decrease in entropy; at high temperatures

B. An exothermic reaction; an increase in entropy; at any temperature

C. An endothermic reaction; an increase in entropy; at low temperatures

D. An endothermic reaction; a decrease in entropy; at any temperature

Answer 1

The conditions that result in a spontaneous reaction are an exothermic reaction with an increase in entropy, and this can occur at any temperature.

Step-by-step explanation:

The set of conditions that would result in a spontaneous reaction is: B. An exothermic reaction; an increase in entropy; at any temperature. This is because a spontaneous reaction often involves a decrease in enthalpy (ΔH), which is characteristic of exothermic reactions, and an increase in entropy (ΔS), meaning the disorder of the system increases. According to the second law of thermodynamics, all spontaneous processes result in increased or constant total entropy of a system. A reaction that is exothermic and has an increasing entropy will tend to have a negative Gibbs free energy (ΔG), which indicates a spontaneous process. This is corroborated by real-life examples such as combustion and the fact that some endothermic reactions can also be spontaneous at high temperatures because they have a favorable entropy change.

Answer 2

Answer: The correct answer is Option B.

Step-by-step explanation:

For a reaction to be spontaneous, the Gibbs' Free Energy must be negative.

Equation for Gibbs Free energy is given by:

`G=H-TS`

Where, G = Gibbs free energy

H = Enthalpy of the reaction

T = Temperature of the system

S = Entropy of the system

Sign convention for all the quantities:

For H: It is negative for exothermic reactions and positive for endothermic reactions

For S: It is positive when there is increase in entropy and it is negative when there is decrease in entropy.

If we want G to be negative, the conditions necessary are:

`G=(-ve)-(+ve)=-ve`

The product of temperature and entropy must be positive and that will be positive when there is increase in entropy at any temperature.

Hence, the correct answer is Option B.