posted by Sam on .
In a previous
experiment, 0.800 g of the green complex iron salt was placed in an Erlenmeyer flask and
heated with concentrated sulfuric acid until all oxalate ion was destroyed (CO2, SO2 and
H2O are formed). Ferric ion (Fe3+) remained in solution and was reduced to Fe2+ by reaction
with Al wire. The ferrous ion (Fe2+) was then titrated with KMnO4 solution according to
equation (2) and 32.60 mL of 0.0100 M permanganate solution was required to reach the
endpoint. The blank required 0.03 mL of the permanganate solution. Find the mass % of
iron in the complex salt.
Equation 2 is Fe2+ (aq) + MnO4
–(aq) Fe3+(aq) + Mn2+(aq)
Concentration of KMnO4 is 0.0082003124
moles KMnO4 = M x L
Using the coefficients in the balanced equation, convert moles KMnO4 to moles Fe^+2.
Convert moles Fe to grams. grams = moles x molar mass.
%Fe = (g Fe/0.8)*100 = ??
NOte that there is a blank of 0.03 mL; therefore, the volume of KMnO4 is 32.60 mL - 0.03 mL and convert that answer to L for the M x L equation above. Note also that the Fe + KMnO4 equation above is not balanced.