Question

Which of the following reactions is
exothermic?
a) H2(g)--------2H(g)
b)C(s) ----------C(g)
c) 2Cl(g)---------Cl2(g)
d) H2O(s)---------H2O(l)​

Answer 1

Option (c) 2Cl(g)→Cl is correct. Entropy is reducing (positive) in the reaction as the number of molecules decreases, which lowers the system's randomness. Since a bond is being made and H is also supplied, the reaction is likewise exothermic.  △H is also −ve.

What is an exothermic reaction:

• Chemical processes known as exothermic reactions generate heat. When heat is transferred from the system to its surroundings, as described in Section II-B of Chapter 3, the heat flow q is considered negative. Therefore, the H of the reaction is negative for exothermic processes.

• Heat is released during an exothermic reaction, raising the temperature of the immediate environment. The environment is cooled through an endothermic process that absorbs heat.

• Aluminum and common iron rust combine to form corundum and molten iron.

• Therefore, a reaction is exothermic and its enthalpy will be negative if it releases more energy than it takes in. Consider this as a certain quantity of heat evaporating from (or being removed from) the reaction. A reaction is endothermic if it absorbs or utilizes more energy than it produces.

Learn more about the exothermic reactions:

1. Example of exothermic reaction​

https://brainly.in/question/23263499?referrer=searchResults

2. Exothermic and exothermic reaction​

https://brainly.in/question/8929280?referrer=searchResults

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