Too Much Indicator in Titration: Causes & Solutions

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In summary: If you had read it, you would know that the salt form is yellow when at a pH of 4 or lower, but will change color to orange at a higher pH. So, the presence of other alkaline material would not affect the color change. So, in this case, adding too much indicator would not be a source of error.
  • #1
man0005
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How would adding too much indicator to a base being titrated by an acid affect the result?
Can I list it as a possible error?
If not, can someone please suggest another one? please also say how it would affect the outcome of the experiment and how i would be able to minimise it.

Thanks :)
 
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  • #2
The indicator itself is either a weak acid or a weak base. Adding too much indicator will force your titration to significantly include the indicator an an interfering analyte component competing with your titrant against the acid or base which you are expecting to measure.

If you can comfortably do the titration monitoring with a pH meter, then you could titrate without a colored indicator.
 
  • #4
we used methly orange
 
  • #5
it can also alter the volume...
 
  • #6
NEILS BOHR said:
it can also alter the volume...

Just what level of material quantity is meant by "too much indicator"? A 100 ml. quantity of titration solution would usually be given no more than about 3 or 4 drops of indicator solution, hardly meaningful to the volume of the contents in the titration vessel. Greater concern for concentration would be from adding maybe 5 or more milliliters of indicator solution, but then of great concern is still how much actual indicator was present in the titration vessel to compete with the actually sought material.

Based on volume alone, I would not expect even 7 to 10 ml. of indicator to mean much; it is the amount of indicator compound that would be more of an interference.
 
  • #7
symbolipoint said:
it is the amount of indicator compound that would be more of an interference.

That's exactly the problem. Changes in volume are rarely important - many titration procedures call for dilution of the sample up to 100 or 200 mL, but it is rarely exact number, so even adding 10 mL more or less doesn't matter.
 
  • #8
so what's the general consensus?
is it a possible error?
what I am mainly concerned is whether or not it would affect a base
being titrated, since the indicator itself is a weak acid.
i know it would affect an acid (it shifts pH)
 
  • #9
Have you read the link provided?
 
  • #10
yeah..doesnt really specify though :/
just says that it will modify the results

sorry i just want to be sure that it is a possible error :S
 
  • #11
Methyl Orange will be in its salt form in alkaline and neutral water solution. The salt form would be yellow, but at about pH 4 and below it will be orange. Some information may be found here: http://en.wikipedia.org/wiki/Methyl_orange

If you had a solution of Methyl Orange but of uncertain concentration, yet high enough to perform a titration, let's say, of the salt form, then the solution would be yellow, probably strong yellow. You would titrate this with an acid to a color change from yellow to orange. You could determine the amount or concentration of the salt-form Methyl Orange in your sample or your solution.

Now, what if your alkaline Methyl Orange solution had a small amount of some other alkaline material present and you titrate with your acid titrant? Your color change pH transition may now depend on two materials: the large amount of Methyl Orange salt, and your other alkaline material. One or both of these materials may have steep pH changes either near or at pH 4.
 
  • #12
so...in simple terms..?
would it be a source of error?
 
  • #13
so in this case, would be right in saying that adding too much indictor would be a source of error since it is a weak acid and would react with the base being titrated, thus affecting the end point determined.

Or should i say something about the pH?
 
  • #14
man0005 said:
so in this case, would be right in saying that adding too much indictor would be a source of error since it is a weak acid and would react with the base being titrated, thus affecting the end point determined.

You should try to evaluate how large error it can produce, but you are right when it comes to general idea.

Or should i say something about the pH?

Something what?
 
  • #15
as in the fact that it can shift the pH and subsequently the end point?
or does not that apply to this case since it is being added to a base not an acid?
 
  • #16
man0005 said:
as in the fact that it can shift the pH and subsequently the end point?
or does not that apply to this case since it is being added to a base not an acid?

Earlier you stated you have read the page I linked to, now you are asking things which clearly show you didn't.
 

1. What is a titration and how does it work?

A titration is a laboratory technique used to determine the concentration of an unknown solution by reacting it with a known solution. This is done by gradually adding the known solution, called the titrant, to the unknown solution until a chemical reaction occurs. The point at which the reaction is complete is called the endpoint, and it can be determined by using an indicator or measuring the pH of the solution.

2. What is an indicator and why is it used in titration?

An indicator is a substance that changes color when it comes into contact with an acid or a base. In titration, indicators are used to signal when the reaction between the titrant and the unknown solution is complete. This helps to determine the endpoint of the titration and the concentration of the unknown solution.

3. What causes too much indicator in titration?

Too much indicator in titration can be caused by inaccurate measurement of the indicator, or by adding too much of it to the solution. This can lead to an excess of the indicator, which can affect the color change at the endpoint and give inaccurate results.

4. What are the effects of too much indicator in titration?

Too much indicator in titration can cause the endpoint of the titration to be reached prematurely, resulting in an inaccurate measurement of the unknown solution's concentration. It can also affect the color change at the endpoint, making it difficult to determine when the reaction is complete.

5. How can too much indicator in titration be avoided or corrected?

To avoid too much indicator in titration, it is important to accurately measure the amount of indicator needed for the reaction. If too much indicator has already been added, the solution can be diluted with more of the unknown solution or titrant to reach the correct concentration. In some cases, it may be necessary to restart the titration using a new sample and a more precise measurement of the indicator.

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