Jawaban:

Rumus  "Perubahan Entalpi (ΔH)" Berdasarkan "Entalpi Pembentukan Standar (ΔH°f)"

ΔH = (jumlah ΔH°f) produk - (jumlah ΔH°f) reaktan

1. Fe₂O₃ + 3 CO ⇒ 2 Fe + 3 CO₂

ΔH = (2 × ΔH°f Fe + 3 × ΔH°f CO₂) - (ΔH°f Fe₂O₃ + 3 × ΔH°f CO)

ΔH = [2×(0) + 3×(-393,5)] - [ (-822,2) + 3×(-110,5)]

ΔH = [(-1.180,5)] - [(-1.153,7)]

ΔH = -26,8 kj/mol

2. C₃H₈ + 5 O₂ ⇒ 3 CO₂ + 4 H₂O

ΔH = (3 × ΔH°f CO₂ + 4 × ΔH°f H₂O) - (ΔH°f C₃H₈  + 5 × ΔH°f O₂)

ΔH = [3×(-393,5) + 4×(-242)] - [ (-104) + 5×(0)]

ΔH = [(-2,148,5)] - [(-104)]

ΔH = -2.044,5 kj/mol (C)

3. CH₃OH + 3/2 O₂ ⇒ CO₂ + 2 H₂O     ΔH = -638,5 kj

ΔH = (ΔH°f CO₂ + 2 × ΔH°f H₂O) - (ΔH°f CH₃OH  + 3/2 × ΔH°f O₂)

-638,5 = [(-393,51) + 2×(-241,8)] - [ ΔH°f CH₃OH + 3/2×(0)]

-638,5 = [(-877,11)] - [ΔH°f CH₃OH ]

ΔH°f CH₃OH = (-877,11) + (638,5)

ΔH°f CH₃OH = -238,61 kj/mol