Use the bond energies given in the "Bond Energy" table (can be gained from google) to estimate the delta Ho for the reaction given below.
2ClF3(g) + 2O2(g) Cl2O(g) + 3OF2(g)
I did this:
1530 + 996 - (410 + 570) = 1546.
But the answer was wrong. I don't know where I did wrong.
Thanks!
Bonds broken: 6 Cl-F and 2 O=O.
Bonds formed: 2 Cl-O and 6 O-F
delta H = (sum reactants)-(sum products) = delta H rxn.
It is unclear is this is the reaction you want.
To estimate ΔHo for a reaction using bond energies, you need to calculate the energy associated with breaking the bonds in the reactant molecules and the energy associated with forming the bonds in the product molecules.
Here's how you can do it step by step:
1. Write down the balanced chemical equation for the reaction:
2ClF3(g) + 2O2(g) → Cl2O(g) + 3OF2(g)
2. Identify all the bonds that break in the reactant molecules:
In 2ClF3(g), you have 6 Cl-F bonds that need to be broken.
In 2O2(g), you have 4 O=O bonds that need to be broken.
3. Look up the bond energies for the bonds you identified. From the "Bond Energy" table, you provided:
Cl-F bond energy = 410 kJ/mol
O=O bond energy = 570 kJ/mol
4. Calculate the energy needed to break all the bonds in the reactants:
Energy needed to break Cl-F bonds = 6 Cl-F bonds * 410 kJ/mol = 2460 kJ/mol
Energy needed to break O=O bonds = 4 O=O bonds * 570 kJ/mol = 2280 kJ/mol
5. Identify all the bonds that form in the product molecules:
In Cl2O(g), you have 1 Cl=O bond that forms.
In 3OF2(g), you have 6 O-F bonds that form.
6. Look up the bond energies for the bonds you identified:
Cl=O bond energy = 630 kJ/mol
O-F bond energy = 710 kJ/mol
7. Calculate the energy released when all the bonds form in the products:
Energy released when Cl=O bond forms = 1 Cl=O bond * 630 kJ/mol = 630 kJ/mol
Energy released when O-F bonds form = 6 O-F bonds * 710 kJ/mol = 4260 kJ/mol
8. Calculate the energy change (ΔHo) for the reaction:
ΔHo = (Energy needed to break bonds in reactants) - (Energy released when bonds form in products)
= (2460 kJ/mol + 2280 kJ/mol) - (630 kJ/mol + 4260 kJ/mol)
= 4740 kJ/mol - 4890 kJ/mol
= -150 kJ/mol
Therefore, the estimated ΔHo for the reaction is -150 kJ/mol (negative indicates an exothermic reaction).