## bond dissociation energy

Karyn Nguyen 1K
Posts: 72
Joined: Fri Apr 06, 2018 11:04 am

### bond dissociation energy

Calculate $\Delta H^{\circ}_{rxn}$ using bond dissociation energy of:

$H_{2} + Cl_{2}\rightarrow 2 HCl$

H-H = 432 kJ/mol
Cl-Cl = 239 kJ/mol
H-Cl = 427 kJ/mol

Why do we divide the equation by 2 and use $\frac{1}{2}H_{2} + \frac{1}{2}Cl_{2} \rightarrow 1HCl$ to get the right answer which is -91.5 kJ/mol?

Fiona Jackson 1D
Posts: 30
Joined: Fri Sep 28, 2018 12:22 am

### Re: bond dissociation energy

Hi! Because each dissociation energy is given in kJ/mol, you divide the equation by two so you only have to multiply the energy by 1 mole rather than two. In other words, you should be able to get the right answer without dividing, but it just makes calculations easier.

Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

### Who is online

Users browsing this forum: No registered users and 1 guest