Chemistry
posted by walter .
From the following data at 25°C,
H2(g) + Cl2(g) → 2HCl(g) ΔH0 = −185 kJ
2H2(g) + O2(g) → 2H2O(g) ΔH0 = −483.7 kJ
Calculate ΔH0 at 25°C for the reaction below.
4HCl(g) + O2(g) → 2Cl2(g) + 2H2O(g)

Multiply equation 1 by 2 and reverse it. Add to equation 2. That will give you the equation you want but you need to go through the steps to confirm that.
When you multiply an equation, do the same to delta H. When you reverse and equation change the sign of delta H. 
Hai,1no equestion *2, then, 1no2no .
(185483.7)=298.7 ans.ok 
Sorry ans hobe (185*2)483.7=113.7 ans,ok