1
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?
2
IIT-JEE 1980
MCQ (Single Correct Answer)
+2
-0.5
Element X is strongly electropositive and element Y is strongly electronegative. Both are univalent. The compound formed would be
A
X+Y-
B
X-X+
C
X-Y
D
X $$\to$$ Y
3
IIT-JEE 1980
MCQ (Single Correct Answer)
+2
-0.5
Which of the following compounds are covalent?
A
H2
B
CaO
C
KCl
D
Na2S
4
IIT-JEE 1980
MCQ (Single Correct Answer)
+2
-0.5
The total number of electrons that take part in forming the bond in N2 is
A
2
B
4
C
6
D
10
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