The standard enthalpy of formation of NiSO
4(s) at 25 °C is -872.9 kJ/mol. The chemical equation to which this value

◦ 1/2 Ni(s) + 1/2 S(s) + 1/2 O
2(g) → 1/2 NiSO
4(s)
◦ Ni(s) + S(s) + 4 O(g) → NiSO
4(s)
◦ Ni(s) + S(s) + 2 O
2(g) → NiSO
4(s)
◦ Ni(s) + 1/8 S
8(s) + 1/2 O
2(g) → NiSO
4(s)
◦ NiSO
4(s) → Ni(s) + S(s) + 4 O(g)