Chemistry - Thermochemistry Question with Solution | TestHub

Given ΔH is for 16 g O₂ (½ mole), so adjust reactions accordingly.

(P)Reaction uses 5O₂, so for ½ O₂ divide by 10

ΔH = −2801/10 = −280.1 ≈ −285.8

P → (1)

(Q) Already for ½ O₂

ΔH = −285.8 kJ

Q → (1)

(R) Given for 3FeO + ½O₂ → Fe₃O₄

ΔH matches −302.4 kJ

R → (4)

(S) C(graphite) + O₂ → CO₂ = −393.4 kJ

For ½ O₂ → divide by 2 ⇒ −196.7 kJ

S → (2)