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# Re: Volumetric Analysis

Submitted by mandrum56 on Sat, 03/13/2010 - 04:53

Thank you very much for dropping by. I have here 3 questions. Someone please help me answer these questions, because I literally find it hard to answer and I'm failling. please do help me:

1.) How many grams of Oxalic Acid , H2C2O4*2H2O are required to make 1.0L(iters) of 0.5N(ormality) Solution?

2.)A sample of iron ore are weighing 1.1255g(rams) is dissolved. All the iron is reduced to FE2+ and the soulution is titrated with 0.1520 N(ormality) KMnO4. Calculate the % Fe2O3 in the sample. (amount of KMnO4 used is 42.0 mL)

Hint: Fe2O3 --> FeO

3.)A 0.5500g sample of impure MgO is titrated with HCl of which 2.5 mL= 0.0650g of CaCO3. The endpoint is over-stepped on the addition of 50 mL of the acid, and the solution becomes neutral on the further addition of 2.35 mL of 0.3800N NaOH. What is the %MgO in the sample?

I am looking forward that you could be the answer towards my learning.

Oxalic acid is a dibasic acid (it has 2 functional acid group/formula unit)

So to make a 0.5N solution you would need 0.5 equivalents per litre.
The equivalent weight of oxalic acid = molar mass in grams/2e

2. Write two ion electron equations for Fe2+  ----> Fe3+ (oxidation) and MnO4- ---> Mn2+ (reduction).
Find the ratio of equivalents of Fe2+ : MnO4-

From the data on MnO4-, calculate the equivalents of  Fe2+ in the sample.

Relate this back to the formula mass of Fe2O3 knowing that 1 mole of Fe2+ comes from 1/2 mole Fe2O3