Question

1. Caiculate your percent error for the amount of iran in the tablet. T pkismit amount of iron inth" table. The actual amount ofironinth percent-127-3-2751 00-87. 98% error 27 in Part B of the experiment, a student did not wait before recording the purple solution and proceeded to calculate the amount of iron. 2. volume of KMnos added after seeing a While calculating, the solution became coforless. How would this change the calculated amount of iron? Explain how it would difter from the true coloriess. How would amount of iron in the pill.

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Answer 1

Reaction between KMnO4 and Fe2+ is:

MnO4- + 8H+ + 5Fe2+ ---------- Mn+ + 5Fe3+ + 4H2O

The end-point of the titration is a pale pink color. If the endpoint is passed, then the volume of KMnO4 added would be higher. Since # moles of KMnO4 = moles * Molarity of KMno4, this would give a higher value for the # moles of KMnO4, say 'X' moes.

As per the reaction, 1 mole of MnO4- reacts with 5 moles of Fe2+. Therefore, the # moles of Fe2+ corresponding to the volume of KMnO4 added would also be higher i.e X*5. This would then over estimate the value of iron in the pill than the true value.