How do i calculate the standard enthalpy change for the following reaction?

I am trying to understand the standard enthalpy change.





I am asked





Using the values from Appendix C, calculate the standard enthalpy change for each of the following reactions:


(a) 2SO2 (g) + O2 (g) --%26gt; 2 SO3 (g)





From the appendix, i find that 2SO2 = 2*(-296.9) = -593.8


and of course O2 is nothing


2 SO3 = 2*(-395.2) = -790.4


from what i understand i just take the left side and find the difference between the 2.





would the answer be ΔH= -196.6kJ? or 196.6kJ? thanks for the help.

How do i calculate the standard enthalpy change for the following reaction?
ΔHreaction = (sum of ΔHf for products) - (sum of ΔHf for reactants)


So,


ΔH = -790.4 -(-593.8) = -196.6 kJ/mol

rosemary