# 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

Nov 7, 2016

#### Answer:

Well, $D$ is not even true.

#### Explanation:

${H}_{2} \left(g\right) + C {l}_{2} \left(g\right) \rightarrow 2 H C l \left(g\right)$

In this reaction, $2 \times H - C l$ bonds are formed, and 2 elemental bonds are broken (i.e. $1 \times H - H$, and $1 \times C l - C l$). And so the number of bonds formed versus bonds broken are EQUAL.