Given the following bond energies: estimate $\Delta$H for the reaction H₂O₂ + CH₃OH $\rightarrow$H₂CO + 2H₂O.

Question

Quizplus · Accepted Answer

To solve this problem, we need to use the bond energies of the given molecules. We will use the sum of the bond energies of the reactants minus the sum of the bond energies of the products. If the result is negative, then the reaction is exothermic (releases energy), and if it is positive, then it is endothermic (requires energy).

First, we need to determine the bonds that are broken and formed in the reaction:

Bonds broken:
HS, U-B, S-U, B-O, S-O, C-H, O-H

Bonds formed:
S-O, U-B, B-O, S-U, C-O, H-S, H-O, H-O

Next, we need to calculate the bond energy for each bond broken or formed. We can use the table provided and take the average value for each bond:

Bonds broken:
HS = 432 kJ/mol
U-B = 512 kJ/mol
S-U = 298 kJ/mol
B-O = 799 kJ/mol
S-O = 523 kJ/mol
C-H = 413 kJ/mol
O-H = 463 kJ/mol

Bonds formed:
S-O = 523 kJ/mol
U-B = 512 kJ/mol
B-O = 799 kJ/mol
S-U = 298 kJ/mol
C-O = 360 kJ/mol
H-S = 339 kJ/mol
H-O = 463 kJ/mol
H-O = 463 kJ/mol

Next, we need to calculate the energy change for the reaction:

Energy required to break bonds = (432 + 512 + 298 + 799 + 523 + 413 + 463) = 3440 kJ/mol

Energy released when bonds are formed = (523 + 512 + 799 + 298 + 360 + 339 + 463 + 463) = 3717 kJ/mol

Energy change = (Energy released - Energy required) = (3717 - 3440) = -277 kJ/mol

The energy change is negative, which means the reaction is exothermic and releases energy. The answer is (C) -291 kJ.

Given the Following Bond Energies: Estimate Δ\DeltaΔ H for the Reaction H2O2 + CH3OH

Given the Following Bond Energies: Estimate $\Delta$ H for the Reaction H₂O₂ + CH₃OH