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painted frequently
(ii) Find out the oxidation number of Mn inKMnO4.
Sol. (O.N. of K) + (ON of Mn)
+4*(ON of O) = 0
1 + Mn + 4* (-2) = 0
1 + Mn - 8 = 0
Mn - 7 = 0
ON of Mn = +7
(iii) What happens at cathode and anode in a
galvanic cell?
Ans. Reduction take place at cathode and
oxidation at anode in galvanic cell
ZnZn2+ + 2e-
Cu2+ + 2e-Cu
(iv) What is the difference between the
corrosion and rusting?
Ans. Corrosion: The eating away of a metal
surface by redox reaction is called corrosion,
while corrosion of iron is called rusting
(v) Describe the chemical reaction of alkalineearth metals with hydrogen.
Ans. Reaction of alkaline earth metal with
hydrogen is
1. Mg + H2
Mg Hz
2. Ca + H2
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(vi) Why does Electropositivity increase fromtop to bottom in a group?
Ans. The electropositivity increases down the
group due to increase in atomic size.
(vii) What is colour of lodine and Bromine?
Ans. The color of iodine is purple and that of
Bromine is raddish brown
(viii) Why silver and gold are least reactive?
Ans. Silver and gold are least reactive because
they do not lose electrons easily.
(Part - 11)
05.(a) One the postulates of Bohr's atomic
model is that angular momentum of a
moving electron is quantized. Explain its
meaning and calculate the angular
momentum of third orbit (i.e. n=3)
(b) Define the following:
(1) Atom
(ii) lon
(iii) Free radicals (iv) Molecule
