Finding indicator for acid-base titration

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    Titration
In summary, at the endpoint of the titration, phenolphthalien will show a color change in an ammonia solution. This change will correspond to the pH of the solution.
  • #1
haha0p1
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Homework Statement
Suggest a suitable indicator to find the end-points of the reaction below:
0.0500 mol/dm³ nitric acid and 0.0500 mol/dm³ aqueous ammonia.
Relevant Equations
Acid + Base = Salt + Water
This question is asking about finding the indicator. I think phenolphthalein will be used as there is a reaction between strong acid and strong base. Is this approach to the question correct? Or am I missing any important concept? Kindly tell
 
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  • #2
Ammonia solution is not a strong base...
What is the pH of ammonia, nitric acid and ammonium nitrate (the end product)
Check the pH that phenolphthalien changes colour at.
What colour will it show in the ammonia solution?
What colour will it show at the end point of the titration?
 
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  • #3
DrJohn said:
Ammonia solution is not a strong base...
What is the pH of ammonia, nitric acid and ammonium nitrate (the end product)
Check the pH that phenolphthalien changes colour at.
What colour will it show in the ammonia solution?
What colour will it show at the end point of the titration?
Ammonia is a weak base and nitric acid is a strong acid. Will methyl red be used?
 
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  • #4
haha0p1 said:
Ammonia is a weak base and nitric acid is a strong acid. Will methyl red be used?
That would depend on the pH around the equivalence point.
 
  • #5
Mayhem said:
That would depend on the pH around the equivalence point.
This is a two mark question. Can you tell how we will approach questions like this one.
 
  • #6
haha0p1 said:
This is a two mark question. Can you tell how we will approach questions like this one.
So this is a homework question. How do you like this idea: Try to perform a titration of a strong acid with ammonia solution. Monitor the entire titration with a pH meter. Find the inflection point pH. Making a graph might be needed. Now find a table of pH indicators and choose an indicator which has a color transition as near to the pH inflection point found, as you can find.
 
  • #7
haha0p1 said:
Homework Statement:: Suggest a suitable indicator to find the end-points of the reaction below:
0.0500 mol/dm³ nitric acid and 0.0500 mol/dm³ aqueous ammonia.
Relevant Equations:: Acid + Base = Salt + Water

This question is asking about finding the indicator. I think phenolphthalein will be used as there is a reaction between strong acid and strong base. Is this approach to the question correct? Or am I missing any important concept? Kindly tell
I could use some correction in case my thinking is wrong, but I would tend to agree here, to use phenolphthalein. Color change is at pH above 7 (but I not sure; I should really look-up this information). Full neutralization of ammonia would be at something above pH 7.
 

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