1
IIT-JEE 1983
Subjective
+5
-0
The density of a 3 M Sodium thiosulphate solution (Na2S2O3) is 1.25 g per ml. Calculate

(i) the percentage by weight of sodium thiosulphate,

(ii) the mole fraction of sodium thiosulphate and

(iii) the molalities of Na+ and $$S_2O_3^{-2}$$ ions
2
IIT-JEE 1982
Subjective
+4
-0
Hydroxylamine reduces iron (III) according to the equation:

2NH2OH + 4Fe3+ $$\to$$ N2O(g) $$ \uparrow $$ + H2O + 4Fe2+ + 4H+

Iron (II) thus produced is estimated by titration with a standard permanganate solution. The reaction is :

$$MnO_4^-$$ + 5Fe2+ + 8H+ $$\to$$ Mn2+ + 5Fe3+ + 4H2O

A 10 ml sample of hydroxylamine solution was Diluted to 1 litre. 50 ml of this diluted solution was boiled with an excess of iron (III) solution. The resulting solution required 12 ml of 0.02 M KMnO4 solution for complete oxidation of iron (II). Calculate the weight of hydroxylamine in one litre of the original solution. (H = 1, N = 14, O = 16, K =39, Mn = 55, Fe = 56)
3
IIT-JEE 1981
Subjective
+3
-0
A 1.00 gm sample of H2O2 solution containing X percent H2O2 by weight requires X ml of a KMnO4 solution for complete oxidation under acidic conditions. Calculate the normality of the KMnO4 solution.
4
IIT-JEE 1980
Subjective
+4
-0
(a) One litre of a sample of hard water contains 1 mg of CaCl2 and 1 mg of MgCl2. Find the total hardness in terms of parts of CaCO3 per 106 parts of water by weight.

(b) A sample of hard water contains 20 mg of Ca++ ions per litre. How many milli-equivalent of Na2CO3 would be required to soften 1 litre of the sample?

(c) 1 gm of Mg is burnt in a closed vessel which contains 0.5gm of O2.
      (i) Which reactant is left in excess?
      (ii) Find the weight of the excess reactants.
      (iii) How many milliliters of 0.5N H2SO4 will dissolve the residue in the vessel?
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