A 2.893 g unkown sample contains iron in the form of the Fe^+2 ion. When the sam

Question

A 2.893 g unkown sample contains iron in the form of the Fe^+2 ion. When the sample is dissolved and an a RedOx titration is performed, 28.45 mL of 0.01971 M KMNO_4 is required to arrive at the red colored end point. The reaction is shown for the iron reacting with permanganate. The number of moles of Fe^+2 ion determined is moles Fe^+2. A 2.893 g unkown sample contains iron in the form of the Fe^+2 ion. When the sample is dissolved and an a RedOx titration is performed, 28.45 mL of 0.01971 M KMNO_4 is required to arrive at the red colored end point. The reaction is shown for the iron reacting with permanganate. The number of grams of Fe^+2 ion determined is grams Fe^+2.

Explanation / Answer

The balance reaction between Fe^2+ and KMnO4 is : 5Fe^2+ + MnO4^- + 8H^+==> 5Fe^3+ + Mn^2 + + 4H2O

5 moles of Fr^2+ reacts with 1 mole of MnO4^-

moles of KMn O4 used in the titration = 0.01971 M *0.02845 L = 5.6*10^-4 moles

moles of Fe^2+ in the sample = 5*5.6*10^-4 = 2.8*10^-3 moles

mass of Fe^2+ = 2.8*10^-3 moles* 56 gm/mol = 0.1570 gm

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