Pre-laboratory Questions: Week io, Electrochemistry When titrating KMno4 against

Question

Pre-laboratory Questions: Week io, Electrochemistry When titrating KMno4 against C2042- the solution turns purple initially with just a few drops of permanganate, then becomes nearly colorless, before eventually becoming pink at the endpoint. Please explain these changes in color based on the chemistry in the lab. A 48.36 mL aliquot of aqueous KMno4 was used to titrate o.317o g of Nazczo4. What is the molarity of the potassium permanganate solution? The a or m moles NavCrou is o 313o. mol 2 mmel NouC (2.306mmol)KMnO4 In the event of a fire in the building during your experiment this week, what would you do if you were in the middle of a reaction?

Explanation / Answer

Question 1.

The color of MnO4- in solution is purple

C2O4-2 is colorless

therefore, when few drops of KMnO4 are added, they will intially be shown in purple color

then MnO4- will react with C2O4-2, so it changes oxidation state to Mn+7

Mn+7 is purple, but since there is still plenty of C2O4-2

Eventually, C2O4-2 will react completely from MnO4-2

after this, thre is plenty of Mn+7 which is pink

this explains the change of colors

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