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Topic: Enthalpy of Reaction  (Read 8257 times)

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Offline washey

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Enthalpy of Reaction
« on: May 29, 2008, 02:12:50 AM »
In my lab we are working the neautralization of HCl with NH3.
We are asked for the enthalpy of reaction, per mole of HCl and NH3.

I have:
Qreaction = 254.5j
Moles of HCl in 25mL of 2M HCl solution = 0.005 mole
Moles of NH3 in 25mL of 2M NH3 solution = 0.005 mole

How do I come up with the enthalpy of reaction per mole of each from this?

Offline tamim83

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Re: Enthalpy of Reaction
« Reply #1 on: May 29, 2008, 09:29:17 AM »
First, write a balanced chemical equation (you don't really need it in this case but it is a very good habit to have)

Enthalpy is the heat released or absorbed at constant pressure. 

Does that help?

Offline washey

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Re: Enthalpy of Reaction
« Reply #2 on: May 29, 2008, 10:17:49 AM »
Not really. My brain is scrambled right now. I am sure I have all the info, but just can't figure out which formula I need to come up with the answer. I can't seem to find any examples in my text book to direct me. Do I need the individual Delta Hfusion, for each? If even after that, I am still not sure about the rest of the formula.

Delta H = ???

Offline Gerard

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Re: Enthalpy of Reaction
« Reply #3 on: May 29, 2008, 10:44:49 AM »
a reaction of HCl and NH3...
first try to solve a balance equation what is the product produce by the reaction....
2HCl+2NH3------>2NH3Cl+H2?
what did you observe during the experiment?
did the test tube cooled? did it heated up?
once you get this you can determine if the reaction is exothermic or exothermic then solve for the heat of reaction....
that is delta H=entalphy of the product - entalphy of the reactants
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Offline washey

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Re: Enthalpy of Reaction
« Reply #4 on: May 29, 2008, 10:56:42 AM »
The equation is: HCl + NH3 --> NH4Cl  with a DeltaT equal to a 21 DegC increase to 31.39 Degc. DeltaT = 10.39, and the system absorbed the heat. My question is, does the enthalpy come from my numbers or from a chart? If my numbers, should they match the chart? What is the formula for this?

Offline Gerard

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Re: Enthalpy of Reaction
« Reply #5 on: May 29, 2008, 11:19:03 AM »
then try to differenetiate what you obtain from what is already established....
is there a great difference or is the numerical difference quite small...
its just like differentiating empirical results with theoritical results....
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Offline tamim83

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Re: Enthalpy of Reaction
« Reply #6 on: May 30, 2008, 09:56:24 AM »
Enthalpy per mole = Heat (q) released or absorbed per mole

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