Calculate the enthalpy of formation of anhydrous aluminium chloride, `Al_(2)Cl_(6)` from the following data :
(i) `2Al(s) + 6HCl (aq) to Al_(2)Cl_(6) (aq) + 3H_(2)(g), Delta_(r)H^(@) = -1004.0 kJ`
(ii) `H_(2)(g) + Cl_(2)(aq) to 2HCl(g) , Delta_(r)H^(@) = -183.9 kJ , Delta_(r)H^(@) = -183.9 kJ`
(iii) `HCl(g) + aq to HCl(aq), Delta_(r)H^(@) = -73.2 kJ`
`Al_(2)Cl_(6)(s) + aq to Al_(2) Cl_(2)(aq) , Delta_(r)H^(@) = -643.0 kJ`

Answer

`-1352.6kJ mol^(-1)`

Explanation

Aim `: 2 Al(s) 3Cl_(2)(g) rarr Al_(2)Cl_(6)(s), DeltaH = ?`
Eqn. `(I ) + 3 xx `Eqn. (ii) - Eqn. (iv) `+ 6 xx` Eqn. (iii) gives the required result.