Calculate the standard enthalpy of the reaction,
`2Fe(s) + 3//2 O_2(g) to Fe_2O_3(s)`
Given :
i.`2Al (s) + Fe_2O_3(s) to 2Fe(s) + Al_2O_3(s), Delta_r H^0 = -847.6kJ`
ii. `2Al(s) + 3//2O_2(g) to Al_2O_3(s), Delta_r H^0 = - 1670 kJ`

Explanation

Reverse Eq.(i) and then add to Eq. (ii)