To calculate the **ΔH° _{rxn}** using

$\overline{){\mathbf{\u2206}}{{{\mathbf{H}}}^{{\mathbf{o}}}}_{\mathbf{r}\mathbf{x}\mathbf{n}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}{{\mathbf{H}}}_{\mathbf{b}\mathbf{o}\mathbf{n}\mathbf{d}\mathbf{}\mathbf{r}\mathbf{e}\mathbf{a}\mathbf{c}\mathbf{t}\mathbf{a}\mathbf{n}\mathbf{t}\mathbf{s}}{\mathbf{}}{\mathbf{-}}{\mathbf{}}{{\mathbf{H}}}_{\mathbf{b}\mathbf{o}\mathbf{n}\mathbf{d}\mathbf{}\mathbf{p}\mathbf{r}\mathbf{o}\mathbf{d}\mathbf{u}\mathbf{c}\mathbf{t}\mathbf{s}}}$

Let’s first figure out what kind of bonds and how many moles are present in each reactant and products because the given bond energies are per mole.

__Balanced Reaction__: H_{2}(g) + I_{2}(g) → 2 HI(g)

**always make sure that the given reaction is balanced*

From the bond energies given below, estimate the ΔH° for the reaction:

H_{2}(g) + I_{2}(g) → 2HI(g)

Bond energies (kJ/mol):

H–H = 436

H–I = 297

I–I = 151

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

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