Questions about TITRATION?
Predict the effect of the each of the following conditions on the calculated MOLARITY of NaOH:
1. The burette to be used was not rinsed with the NaOH solution.
2. The air space at the burette tip was not removed before titration.
3. The flask used to weigh KHP (potassium hydrogen phthalate - a primary standard) contained traces of NaOH.
4. The burette reading for NaOH was taken after rapid delivery of titrant.
Please help me. I WILL definitely give 10 points to the best answer.
Thank you very MUCH.
Answer:
1-if the burette was not rinsed with NaOH the solution will be diluted further due to water drops in the burette giving an in accurate answer .
2-if the air space was not removed the volume which is read is wrong because the volume of the burette is measured from very bottom to the graduation mark so NaOH used is not exactly what you are reading
3-the NaOH will react with KHP making less moles of KHP which means when you carry out the experiment you assume that you have 'X' moles but acctually you have less and you dont realize it . This interefers when you are calculating giving wrong numbers .(calculation formula : M1 x V1/n1=M2xV2/n2
where M is molarity and V is volume and n is the ratio of substances in the formula of reaction )
4-If it were rapid then you would not have an exact end point which means that you dont know exactly how much NaOH reacted with KOH and you think NaOH used was more so it affects your calculation .
In general any precaution in titration is to avoid inaccuracy and improve accuracy as much as possible .
I think this will be what will happen...
1. I'm not particularly sure about this...Considering that you will use NaOH as the titrant, you need to rinse the burette with the titrant to "wash off" any compounds that might react with NaOH if you directly place it on the burette, and will affect the amount you have to drop before you reach the endpoint.
2. The air space will add error to the measurement. It will do so because the air space will be filled before dropping on the analyte (which will deduct a few mL from the reading in the burette). Since molarity=moles/liter, we all get the point.
3. Again, I am not sure of this... but if you are to use a primary standard (which is to serve as "control"/basis of comparison because it has a known measure of the concentration of the analyte), it must be of sufficient purity to ensure that the known concentrations of the analyte would not change... (NaOH might probably again confound the results, considering that KHP is acidic and is sensitive at that). If you compare it to acid-base titrations of NaOh and a certain analyte... well.
4. The titrant has to be dropped slowly becuase most titration indicators are sensitive to even a slight change in pH (I think becuase a slight change in pH is a lot...). If you drop it too rapidly, you will probably miss the endpoint. In this case, you have added more than enough concentration of the titrant to reach endpoint, and you get a higher concentration reading.
I hope I was of help.
hehe, chem16? kulang kasi sa details like baka di nila alam kung sa'n galing ung KHP, anyway, di pa rin ako tapos! hehe...
The answers post by the user, for information only, FunQA.com does not guarantee the right.
More Questions and Answers: