Anouk L.

asked • 09/22/18

How can you correct if you do not determine the precipitation of Ag2CrO4 at the stoichiometric point?

 With the Mohr method

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J.R. S. answered • 09/22/18

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To my knowledge, the Mohr method involves determining chloride concentration by precipitating with silver nitrate.  Not sure what you question is when you mention silver chromate.  Is that a co-precipitate? A little more information would be helpful.
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Anouk L.

We start off with an AgNO3 solution and pipette 10 mL into a conical flask and dilute it with demineralized water to about 100 ml. Add small quantities of NaHCO3 until effervescence ceases. After this we titrate with Ag2CrO4.
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09/22/18

J.R. S.

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Yes, you are correct, and I now think I understand what you are doing.  The determination of chloride ion in the presence of potassium chromate makes the detection of the end point easier to see since the end point will be marked by the first appearance of Ag2CrO4 precipitate which is red in color.  This necessitates that some small excess of Ag+ is added prior to precipitation.  To correct for this, one can use a blank and titrate a solution of K2CrO4 with your standard AgNO3 solution.
 
 
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09/22/18

Anouk L.

Thank you for helping me, now I understand it. Also sorry for posting empty comments but for some reason I can't see the comments until I post one myself.
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09/22/18

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