Class 12 > PYQ CHEMISTRY > 2020 > Set 3

2020

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Q26
Account for the following :
(a) Sulphurous acid is a reducing agent.
(b) Fluorine forms only one oxoacid.
(c) Boiling point of noble gases increases from He to Rn.
OR
Complete the following chemical reactions :
(a) MnO₂+ 4HCl —>

(b) XeF₆+ KF —>

(c) I⁻ (aq) + H⁺ (aq) + O₂(g) —>

Q28
How will the rate of the reaction be affected when
(a) Surface area of the reactant is reduced,

(b) Catalyst is added in a reversible reaction, and

(c) Temperature of the reaction is increased?

Q29
Give the structures of A and B in the following sequence of reactions :
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OR
(a) How will you distinguish between the following pairs of compounds :
(i) Aniline and Ethanamine
(ii) Aniline and N-methylaniline

(b) Arrange the following compounds in decreasing order of their boiling points :
Butanol, Butanamine, Butane

Q30
Give the plausible explanation for the following :
(a) Glucose doesn’t give 2,4-DNP test.
(b) The two strands in DNA are not identical but are complementary.
(c) Starch and cellulose both contain glucose unit as monomer, yet they are structurally different.

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