How would the following action affect your calculated value of the molarity of t

Question

How would the following action affect your calculated value of the molarity of the unknown oxalic acid:

STEP 14: Addition of 3 drops of KMnO4 gave a deep purple which remained. You did not correct for this error.

If it helps, step 14 from my lab manual is as follows:

When you think you have reached the end point, weigh the well plate and record the mass on the REPORT FORM (14). You may add part of a drop of KMnO4 to the well by touching a partial drop to the end of the stirring rod and then stir. An intense pink coloration indicates that you have exceeded the end point. (If the color fades away before 30 seconds, you have not reached the end point and you should repeat this step.)

Explanation / Answer

Potassium permanganate, KMnO4, is a strong oxidizing agent. Permanganate, MnO4

-

, is an intense dark

purple color. Reduction of purple permanganate ion to the colorless Mn+2

ion, the solution will turn from

dark purple to a faint pink color at the equivalence point. No additional indicator is needed for this

titration. The reduction of permanganate requires strong acidic conditions.

In this experiment, permanganate will be reduced by oxalate, C2O4

2-

in acidic conditions. Oxalate reacts

very slowly at room temperature so the solutions are titrated hot to make the procedure practical. The

unbalance redox reaction is shown below.

MnO4 -+ C2O42- ? Mn2+ + CO2 (acidic solution)

In part I of this experiment, a potassium permanganate solution will be standardized against a sample of

potassium oxalate. Once the exact normality (eq/L) of the permanganate solution is determined, it can

be used as a standard oxidizing solution. In part II of this experiment, the standard permanganate

solution will be used to find the concentration of iron(II) in a ferrous solution (g/L). The unbalanced

redox reaction is shown below.

MnO4- + Fe2+ ? Mn2+ + Fe3+

(acidic solution)

the recation acctually ....occurs at high temperature , but when we add 2-3 drops of KMnO4 gave a deep purple which remained.because the reaction needs some activation energy (it take fro heating ) .... soo eventually when its streed it will again color fades away .................so we need to reapeat the step 14 , untill each and ever ion particiapate in the reation

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