Posted by walter on .
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)

Chemistry 
DrBob222,
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. 
Chemistry 
Algebra of sets,
Hai,1no equestion *2, then, 1no2no .
(185483.7)=298.7 ans.ok 
Chemistry 
Algebra of sets,
Sorry ans hobe (185*2)483.7=113.7 ans,ok