Question

Considering entropy (s) of a thermodynamic parameter, the criterion for the spontaneity of any process is,
A. \[\Delta {S_{system}} + \Delta {S_{surroundings}} > 0\]
B. \[\Delta {S_{system}} - \Delta {S_{surroundings}} > 0\]
C. \[\Delta {S_{system}} > 0\]
D. \[\Delta {S_{surroundings}} > 0\]

Answer 1

Hint:The reaction in which product formation occurs at the same conditions in which the reaction occurred is termed spontaneous reaction. One example of this process is a roaring bonfire.
Complete step by step answer:
Let's understand what entropy is. The disorder in a system is termed entropy. The higher the disorder of a system, the higher the measure of entropy. The entropy is symbolically represented by S.
Now, we will understand the second thermodynamic law. According to this law, there is an entropy increase in the universe due to the change of entropy. Mathematically this law is represented by the following equation.
A process is spontaneous only when there is an increase in the entropy of the universe. So, for a spontaneous process,
\[\Delta {S_{system}} + \Delta {S_{surroundings}} > 0\] or \[\Delta {S_{universe}} > 0\]

Hence, option A is correct.

Additional Information:
Let’s understand the 1^st law of thermodynamics. It says the difference between the addition of heat to the system and work completed by the system gives the system's internal energy change. The mathematical representation is,
\[\Delta U = Q - W\]
Here, Q is heat and W is work and \[\Delta U\] is internal energy change.

Note: It is also to be noted a spontaneous process happens automatically. It does not require the energy input for the reaction to occur. They possess a tendency in a strong manner to proceed in one direction. For example, the formation of hydrogen chloride is a spontaneous reaction at all temperatures.