1. Ok, you have the number of moles of oxalic acid used.
You know from your equation that 5 moles of oxalic acid react with 2 moles of MnO4^-.
Can you now guess the number of moles of MnO4^-?
2 C2O4^2- -> 5 MnO4^-
0.002 C2O4^2- -> ? MnO4^-
Then, you know the number of moles of MnO4^- in 43 cm^3. Find the number of moles in 1000 cm^3.
2.
Is the concentration of KMnO4 130 M!
Same thing here. You know from your equation that 5 moles of iron (II) react with one mole of MnO4^-.
1 MnO4^- -> 5 Fe^2+
3.0 MnO4^- -> ? Fe^2+
[provided the concentration of MnO4^- is 130 M]
Then, find the mass of that Fe^2+, with the AW of Fe.
The fraction of Fe^2+ in the sample is the weight due to Fe^2+ over the total weight. The percentage is that fraction, multiplied by 100%. |