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### Topic: Acid and base reactions  (Read 3922 times)

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#### senna

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##### Acid and base reactions
« on: March 29, 2005, 02:54:34 PM »
Below is the question that I am working on.  Will someone check my work for part (a) and (b).  I am also in need of some help on parts (c) and (d).  The questions I Have are below.

The question is: A person mixes 50.0ml of 0.115 M HAc with 25.0 ml of 0.182 M NaOH and then dilutes the resulting mixture to 100.0ml.

a. Write the net ionic equation-----HC2H3O2(aq) + NaOH
NaC2H3O2(aq) + H20[/b]
b. Determine which reagent is in excess. I determined that it is the HC2H3O2 that is in excess and the NaOH that is the limiting reagent.
HC2H3O2=0.00575mol
NaOH= 0.00455mol
c. Calculate the concentration of HC2H3O2, C2H3O2 and Na in the final solution.

[NaAc] [H2o]
•
• [/u]
[HAc] [NaOH]           =  [ 0.0455-x]   [0.0455-x]  =

I know that the Ka for HC2H3O2 is 1.8x10^-5
I am not sure how to figure out the number that I should make the above equation that I figutred out equal to.  If someone could explain this to me that would be great.

d. Calculate the concentration H+ (aq) in this solution.

I know that in this problem I am dealing with:
H+  C2H3O2  Na  OH and H2O.
The H+ from the C2H3O2 would be the only major contributor of H+ ions to the initial solution because the H2O acts either as a weak acid or weak base.  These are my thoughts on this problem so far.  I am not exactly sure of where to go from here.

I am thinking that maybe I should set up the problem where

[H+] [C2H3O2] = Ka for HC2H3O2  Ka =1.8*10^-5
HC2H3O2

Does this make sense to you? Then I would calculate it out for x where H+ equals x.

Thank you for your time and *delete me*!!
It is very much appreciated!

#### Borek

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##### Re:Acid and base reactions
« Reply #1 on: March 29, 2005, 05:41:11 PM »
a. I doubt what you wrote is a net ionic equation Na+ is a spectator.

b. OK

c. Try simple stoichiometry - you know amounts of acid and base mixed.

d. This is classic case for Henderson-Hasselbalch equation.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

#### senna

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##### Re:Acid and base reactions
« Reply #2 on: April 04, 2005, 12:42:48 AM »