Question

Use the reaction equation and bond energies to answer the question.

2H2O → 2H2 + O2

H-O: 467 kJ/mol

H-H: 432 kJ/mol

O=O: 495 kJ/mol

What is the total energy of the reaction? Is this an endothermic or exothermic reaction?

Answer 1

Answer:

It's not any kind of reaction. This is the decomposition/electrolysis reaction: 2H2O=2H2+O2 and this is the synthesis/combustion/oxidation reaction:2H2+O2=2H2O.

Explanation:

It is an endothermic

Answer 2

Bond energy is the measure of a bond's strength; the bigger the bond energy

Enthalpy of reaction = Sum of bond enthalpies of reactant - Sum of bond enthalpies of product

Enthalpy of reaction

2$H_{2}$ + $O_{2}$ ⇒ 2$H_{2}$O

In this reaction, 2 H-H bonds and  O = O bond are broken and 4 0 - H bonds are formed.

Thus,

Δ H = [2 × (Bond enthalpy of H-H bond) + (Bond enthalpy of O=O bond) ] -  

         [ 4 × (Bond enthalpy of O-H bond) ]

ΔH = 2 × 435 KJ + 498 KJ - 4 × ( Bond enthalpy of O-H bond)

ΔH = -571 KJ

∴ 4 × ( Bond enthalpy of O-H bond) = ( 571 + 870 + 498) KJ  = 1939 KJ

Bond enthalpy of O-H bond = (1939/4) = 484.75 KJ

Hence, the bond enthalpy of O-H is 484.75 KJ