Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Lt.Pliskin on October 07, 2005, 12:14:56 AM
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Alright, I have three equations I carried out during a lab I did.
Combining HCl and NaOH
HCl + NaOH --> NaCl + H2O
H+(aq) + Cl -(aq) + Na+(aq) + OH-(aq) --> Na+(aq) + Cl-(aq) + H2O(liq)
H+(aq) + OH-(aq) --> H2O(liq)
Combining Ammonium Chloride and Sodium Hydroxide
NH4Cl + NaOH --> NH3 + NaCl + H2O
NH3(aq) + H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) --> NH3(aq) + Na+(aq) + Cl-(aq) + H20 (liq)
H+(aq) + OH-(aq) --> H2O(liq)
Combining a solution of ammonia (NH3OH) and HCl
NH4OH +HCl --> NH4Cl + H20
NH3(aq) + OH-(aq) + 2H+(aq) + Cl-(aq) --> NH3(aq) + H+(aq) + Cl-(aq) + H2O(liq)
H+(aq) + OH-(aq) --> H20(liq)
Alright, using the heats of reactions obtained from the lab, I came up with:
H+(aq) + OH-(aq) --> H20(liq) -158.23 kJ/mol
H+(aq) + OH-(aq) --> H20(liq) -80.65 kJ/mol
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H+(aq) + OH-(aq) --> H20(liq) -267.54 kJ/mol
My question is, how would I use hess's law to verify that the third one can be found using the heats of reactions of the first two. Usually, a Hess's law problem involves rearranging the reactants and products to get the final quation. How would that work with these?
Any help is greatly appreciated!
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I think maybe all you should have to do is reverse the second equation and add it to the first equation.
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NH4OH is just NH3 and H2O
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So, it would be
Combining a solution of ammonia (NH3OH) and HCl
NH4OH +HCl --> NH4Cl + H20
NH3(aq) + H2O(liq) + H+(aq) + Cl-(aq) --> NH3(aq) + H+(aq) + Cl-(aq) + H2O(liq)
Nothing ---> Nothing?
H+(aq) + OH-(aq) --> H20(liq) -158.23 kJ/mol
H20(liq) --> H+(aq) + OH-(aq) 80.65 kJ/mol
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Nothing --> nothing -267.54 kJ/mol
The two equations cancel each other out, so Im assuming that when NH4OH is added to HCL, no reaction occurs?
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HCl + NaOH ---> NaCl + H2O
NH4OH + NaCl ---> NH4Cl + NaOH
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NH4OH + HCl ---> NH4Cl + H2O
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This is like:
NH3 + HCl ---> NH4+ + Cl-
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OH, ok, I see, thanks!
Now, I have to use net ionic equations witht he calculations, how would those look?
I got:
H+ + Cl- + Na+ + OH- --> H20 + Na+ + Cl-
NH3 + H20 + Na+ + Cl- --> NH3+ H20 + Na+ + Cl-
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NH3 + H20 + H+ + Cl- --> NH3 + H+ + Cl- + H2O which basically means nothing happens :-\
Does the NH4OH dissasociate into those ions? How about the NH4Cl?
Thankyou for your help thus far, I think Ive almost got it! :)
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sorry, we seem to keep missing each other
H+ OH- --> H20
H20 --> H20
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H+ OH- --> H2O
Is this right
**modified to remove spectator ions**
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H+ + NH3 ---> NH4+
You are reacting H+ with NH3 not OH-
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I am totally, lost...
Thanks for your patience with me thus far.
What is the net ionic equation for the NH4CL + NaOH --> NH4OH + NaCl?
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NH4+ + Cl- + Na+ + OH- ----> NH3 + Na+ + Cl- + H2O
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:D Thank you so much! I hope I havent been too much of a bother. I can finally get some sleep now!