Please help me with this-- I don't understand it-- 25 pts! Calculate the change of enthalpy for the reaction 2Al (s) + 3Cl2 (g) --> 2AlCl3 (s) from the following reactions:

Reaction 1: 2Al (s) + 6HCl (aq) --> 2AlCl3 (aq) + 3H2 (g);Change in enthalpy: -1049 kJ

Reaction 2: HCl (g) --> HCl (aq);Change in enthalpy: -74.8 kJ/mol

Reaction 3: H2 (g) + Cl2 (g) --> 2HCl (g);Change in enthalpy: -1845. kJ/mol

Reaction 4: AlCl3 (s) --> AlCl3 (aq);Change in enthalpy: -323. kJ/mol

I have to include the following:

The numerical answer with correct units.

State which reactions, if any, you had to "Flip", or reverse.

State which reactions you had to multiply, if any, to get the correct amount of the compound. Also, include how much you multiplied the reaction by.