Given:
Enthalpy change ΔH for the thermite reaction = -850 kJ
Moles of Al involved = 4
To determine:
Reaction enthalpy when 4 moles of Al reacts
Explanation:
The thermite reaction is-
2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s)
When 2 moles of Al react the enthalpy change is -850 kJ
therefore, when 4 moles of Al reacts, the change in enthalpy is-
= 4 moles * (-850) kJ/2 moles = -1700 kJ
Ans: Enthalpy change is -1700 kJ