Posted by Anonymous on Monday, November 14, 2011 at 7:14pm.
Use the equations with the enthalpy information given below to calculate the ÄH° for the reaction:
S(s) + O2(g) > SO2(g)
S(s) + 3/2 O2(g) > SO3(g)
ÄH° = 395kJ
2 SO2(g) + O2(g) > 2 SO3(g)
ÄH° = 198.2 kJ

Chemistry  DrBob222, Monday, November 14, 2011 at 7:51pm
1) S(s) + 3/2 O2(g) > SO3(g)
ÄH° = 395kJ
2) 2SO2(g) + O2(g) > 2 SO3(g)
ÄH° = 198.2 kJ
Multiply equation 1 by 2 and add to the reverse of equation 2. delta H values are multiplied by any multipliers and delta H values change their sign when the reaction is reversed.
When you finish you will have the right equation EXCEPT it will be just twice what you want; therefore, divide everything by 2 including the delta H value. 
Chemistry  mdc wolfson campus, Monday, November 19, 2012 at 3:51pm
How much heat is evolved when 320 g of SO2 is burned according to the chemical equation shown below?