EXPERIMENT: 10 OXIDATION-REDUCTION TITRATION Name: Date: Instructor Section/Grou
ID: 1049251 • Letter: E
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EXPERIMENT: 10 OXIDATION-REDUCTION TITRATION Name: Date: Instructor Section/Group: Questions (Turn in to your Instructor with the post laboratory report for this experiment) 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.) 1. if you had not rinsed your buret with the stock KMno, solution before beginning the titration? if you thought you reached the end point, but the color faded within 15 seconds and you did not add more KMnO, solution? 2. 3. 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? 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
answer 1 ) if we don't rinse the burret wih kmno4 solution before beginig the titration then the water droplets present inside the burret on putting kmno4 in it will dilute it and its molarity changes ( decreases ) .
answer 2) we know the pink colour means slightly basic. when the flask is open to the contact with air then the CO2 present in the air will dissolve in water and form carbonic acid . The acid will neutralize the OH-, and the color fades . due to this the molarity will increase more naoh is required
M1V1 (kmno4 ) =M2V2 (naoh)
see if V2 increase then the M2V2/V1 value increases due to which kmno4 molarity increases .
answer 4 ) as we put acess of kmno4 according to the expression
M1V1 (kmno4 ) =M2V2 (naoh)
see if V1increase then the M2V2/V1 value decreases due to which kmno4 molarity decreases
answer 5) the reaction is
4 KMnO4(aq) + 6 H2SO4(aq) = 2 K2SO4(aq) + 4 MnSO4(aq) + 6 H2O(l) + 5O2(g)
as the limiting reag ent is H2SO4 and we are also adding water to dillute it the molarity of Kmno4 decreases .
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