EXPERIMENT: 10 OXIDATION-REDUCTION TITRATION Name: Instructor: Date: Post-Lab Qu

Question

EXPERIMENT: 10 OXIDATION-REDUCTION TITRATION Name: Instructor: Date: Post-Lab Questions (Turn in to your Instructor with the post laborator experiment.) y report for this How would your calculation of the molarity of KMno, been affected, if at all: (Clearly explain your reasoning: a simple one-word answer is not sufficient.) . if you had not rinsed your buret with the stock KMnO, solution before beginning the titration 2. if you thought you reached the end point, but the color faded within 15 seconds and you did not add more KMnO, solution? if you had been unable to complete the titration in a single period, but had stored the KMnO solution for several days before returning and picking up where you left off in the experiment without additional standardization? 3. if you had added the KMnO, too rapidly and your end point was an opaque purplish-brown rather than a clear solution with a hint of purple? 4. 5. if you had added twice as much sulfuric acid and water as was called for in the procedure?

Explanation / Answer

1) If the burette is not rinsed with KMnO4 ,then theburette may have left over water that decreases the actual volume of KMnO4 filled in the burette.

V ml of KMnO4 +x ml of water=total volume of burette

concentration of KMnO4=(mol of KMnO4 in V ml)/(Vml+xml) ,so concentration is less(dilution takes place)

Thus, you get decreased concentration of KMnO4.

2) The amount of KMnO4(titrant) added may be less in this case, Volume of KMnO4 (V1) <<< actual volume required for titration

Thus , ( mol of KMnO4 added=Molarity *Volume=M1*V1 ) mol of KMnO4 will be wrongly determined that may give lesser value of concentration of the titre.

M1*V1=M2*V2 (M2=molarity of titre,Volume of titre)

M2=M1*V1/V2

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