Hesse's law

[Awuah29]

Advertisement - Members don't see this ad

Given the following data:

S(s)+ 3/2 O2(g)---SO3(g) deltaH= -395.2 KJ
2SO2(g)+O2----2SO3(g) deltaH= -198.2KJ

Calculate deta H for the reaction
S(s)+ O2(g)---SO2(g)


2 O3(g)----3O2(g) deltaH= -427 KJ
O2(g)------2O(g) deltaH= +495KJ
NO(g)+ O3(g)------NO2(g)+O2(g) deltaH=-199KJ

Calculate delta H for the reaction
NO(g)+O3(g)----NO2(g)


H2(g)+1/2 O2(g)-----H2O(l) deltaH=-285.8KJ
N2O5(g)+H2O(l)------2HNO3(l) deltaH=-76.6KJ
1/2 N2(g)+3/2 O2 (g)+ 1/2 H2(g)----HNO3(l) deltaH+=-174.1KJ

Caculate the delta H for the reaction
2N2(g)+5O2(g)-----2N2O5(g)


I know how to set those problems up, but it seems that I am not getting the answer. Thanks for help!

 

[RozhonDDS]

1) -296.1
2)-412.5
3)-195


They may be right, or be way off

 

[Awuah29]

1) -296.1
2)-412.5
3)-195


They may be right, or be way off

yeah, that sounds right, but how did you set it up? anyone else wanna try?

 

[Futureortho24]

Ok I only had time to do the 1st one and I got the same answer as the previous post: -296.1 here is the explanation:

S+3/2 O2---> SO3

2SO2 + O2--->2SO3

You need to reverse the 2nd equation and multiply it by 1/2:
SO3--->SO2 +1/2 O2 (now the O2's are on opposite sides of the equations and the 1/2 O2 can cancel out with the 3/2 O2 leaving 2/2 O2 which is 1) So since you reversed the 2nd equation, you need to reverse the sign on its corresponding delta H and also multiply that new number by 1/2.

Did that make any sense?!

 

[Awuah29]

anyone, whats to take a shot how to set up 2 and 3?