Question

Why is the reaction H2+Cl2 = 2HCl exothermic?

A: Energy involved in the bonds breaking is greater than that of the bonds forming.
B: Energy involved in the bonds forming is greater than that of the bonds breaking.
C: More bonds are broken than are formed.
D: More bonds are formed than are broken.

I know that Exothermic reactions are bond-forming and the energy involved in bond forming is greater than that of bond breaking. According to my book, the answer is B, but I want to know why D can't be the proper answer.
Thanks

Answer 1

Well, `D` is not even true.

Explanation:

`H_2(g) + Cl_2(g) rarr 2HCl(g)`

In this reaction, `2xxH-Cl` bonds are formed, and 2 elemental bonds are broken (i.e. `1xxH-H`, and `1xxCl-Cl`). And so the number of bonds formed versus bonds broken are EQUAL.