Calculate ΔE in kilojoules per mole for the reaction Atomic masses: , , ) A) 0 B) +2.4 × 10⁶ kJ/mol C) +4.6 × 10⁸ kJ/mol D) -4.6 × 10⁸ kJ/mol E) -2.4 × 10⁶ kJ/mol

Question

Quizplus · Accepted Answer

First, we need to write the balanced equation for the reaction:
2H2(g) + O2(g) → 2H2O(g)

Next, we need to determine the change in energy for the reaction. We can use the bond energy equation:

ΔH = sum of (bond energies broken) - sum of (bond energies formed)

Using bond energy values from a table, we can calculate:

ΔH = [2(436 kJ/mol) + 1(498 kJ/mol)] - [4(432 kJ/mol)] = -484 kJ/mol

Finally, we convert the answer to kilojoules per mole:

ΔE = ΔH/moles of substance involved
moles of substance involved = min(2 mol H2, 1 mol O2) = 1 mol H2
ΔE = -484 kJ/mol ÷ 1 mol = -484 kJ/mol

This corresponds to choice D, which is the only option with a negative value (indicating an exothermic reaction) and a magnitude close to -484 kJ/mol.

Calculate ΔE in Kilojoules Per Mole for the Reaction