Use the molar bond enthalpy data in the table to estimate the value of Δ𝐻∘rxn for the equation CH4(g)+4Cl2(g)⟶CCl4(g)+4HCl(g)

Answer 1

CH₄(g) + 4Cl₂(g)⟶CCl₄(g) + 4HCl(g) ... balanced equation

Bond breaking requires energy

Bond formation releases energy

So, take the difference in bond energy of reactants (bond breaking) and that of the products (bond forming) to get the ∆H of reaction.

Bond energy of reactants:

C-H bond x 4 = bond energy for CH₄

Cl-Cl bond x 4 = bond energy of the 4 mols Cl₂

Add these values together to get bond energy of reactants. This will have a positive number since energy is added

Bond energy of products:

C-Cl bond x 4 = bond energy for CCl₄

H-Cl bond x 4 = bond energy for 4 mols HCl

Add these values together to get bond energy of products. This will have a negative number since energy is released

Take the difference to get the ∆Hºrxn.

Hope this makes sense