## calculating delta H for an expansion

asannajust_1J
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Joined: Wed Sep 11, 2019 12:16 am
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### calculating delta H for an expansion

In problem 4.17, I calculated parts a-d; however do not understand how to obtain delta H for this reaction:
A technician carries out the reaction 2 SO2(g) 1 O2(g) S 2 SO3(g) at 25 8C and 1.00 atm in a cylinder fitted with a piston and maintained at constant pressure. Initially, 0.030 mol SO2 and 0.030 mol O2 are present in the cylinder. The technician then adds a catalyst to initiate the reaction.
a) initial volume =1.47L
b) limiting SO3
c) final volume = 1.1L
d) work = 37.5J
e)enthalpy of reaction?
I used PV=nrt with final volume to find the new temperature, but am not getting -3.3kJ (I have -3.3J)?
f) internal energy of reaction?

Rachel Yu 1G
Posts: 113
Joined: Fri Aug 09, 2019 12:15 am

### Re: calculating delta H for an expansion

You can find the enthalpy by using the standard enthalpies of formation in the back of the textbook. Use equation deltaH = sum of deltaH products - sum of deltaH reactants to find the delta H value.

Alan Cornejo 1a
Posts: 98
Joined: Fri Aug 30, 2019 12:15 am

### Re: calculating delta H for an expansion

Rachel Yu 1G wrote:You can find the enthalpy by using the standard enthalpies of formation in the back of the textbook. Use equation deltaH = sum of deltaH products - sum of deltaH reactants to find the delta H value.

Also a reminder that when using the sum of the deltaH products and reactant it is important to recognize the stoiciometric coefficients as you will need to multiply them by their respective values theyre assigned too

ValerieChavarin 4F
Posts: 99
Joined: Wed Sep 18, 2019 12:18 am

### Re: calculating delta H for an expansion

You'll need to use the standard enthalpy of formation and the ∆Hr° = ∆H° $\sum$(products) - ∆H° $\sum$(reactants)

Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

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