1
IIT-JEE 1992
Subjective
+5
-0
A 2.0 g sample of a mixture containing sodium carbonate, sodium bicarbonate and sodium suplphate is gently heated till the evolution of CO2 ceases. The volume of CO2 at 750 mm Hg pressure and at 298K is measured to be 123.9 ml. A 1.5g of the same sample requires 150 ml. of (M/10) HCl for complete neutralisation. Calculate the % composition of the components of the mixture.
2
IIT-JEE 1992
Subjective
+4
-0
One gram of commercial AgNO3 is dissolved in 50 ml. of water. It is treated with 50 ml. of a KI solution. The silver iodide thus precipitated is filtered off. Excess of KI in the filterate is titrated with (M/10) KIO3 solution in presence of 6M HCl till all I- ions are converted into ICl. It requires 50 ml. of (M/10) KIO3 solution. 20 ml. of the same stock solution of KI requires 30 ml. of (M/10) KIO3 under similar conditions. Calculate the percentage of AgNO3 in the sample.
(Reaction : KIO3 + 2KI + 6HCl $$\to$$ 3ICl + 3KCl + 3H2O)
3
IIT-JEE 1991
Subjective
+4
-0
A 1.0 g sample of Fe2O3 solid of 55.2% purity is dissolved in acid and reduced by heating the solution with zinc dust. The resultant solution is cooled and made upto 100.0 ml. An aliquot of 25.0 ml of this solution requires 17.0 ml of 0.0167M solution of an oxidant for titration. Calculate the number of electrons taken by the oxidant in the reaction of the above titration.
4
IIT-JEE 1991
Subjective
+5
-0
A solution of 0.2 g of a compound containing Cu2+ and $$C_2O_4^{2-}$$ ions on titration with 0.02M $$KMnO_4$$ in presence of $$H_2SO_4$$ consumes 22.6 ml. of the oxidant. The resultant solution in neutralized with Na2CO3, acidified with dil. acetic acid and treated with excess KI. The liberated iodine requires 11.3 ml of 0.05M Na2S2O3 solution for complete reduction.

Find out the molar ratio of Cu2+ to $$C_2O_4^{2-}$$ in the compound.Write down the balanced redox reactions involved in the above titrations.
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