IIT-JEE-Chemistry-Final Revision Set No.66

1. How is boron obtained from borax? Give chemical equations with reaction conditions.

2. When a white crystalline compound X is heated with K2Cr2O7 and concentrated H2SO4 a reddish brown gas A is evolved. On passing A into caustic soda solution, a yellow coloured solution of B is obtained. Neutralizing the solution of B with acetic acid and on subsequent addition of lead acetate a yellow precipitate C is obtained. When X is heated with NaOH solution, a colourless has is evolved and on passing this gas into K2HgI4 solution, a reddish brown precipitate D is formed. Identify A, B, C, D and X.

3. A biologically active compound, Bombykol (C₁₆H₃₀O) is obtained from a natural source. The structure of the compound is determine by the following reactions.
(a) On hydrogenation, Bombykol gives a compound A, C₁₆H₃₄O, which reacts with acetic anhydride to give an ester,
(b) Bombykol also reacts with acetic hydride to give another ester, which on oxidative ozonolysis (O3/H2O2) gives a mixture of butanoic acid, oxalic acid and 10-acetoxy decanoic acid.
Determine the number of double bonds in Bombykol.

4. Two moles of a perfect gas undergo the following processes:
(a) a reversible isobaric expansion from (1.0 atm, 20.0 L) to (1.0 atm, 40.0 L);
(b) a reversible isochoric change state from (1.0 atm, 40.0 L) to (0.5 atm, 40.0 L);
(c) a reversible isothermal compression from (0.5 atm, 40.0 L) to (1.0 atm, 20.0 L);

(ii) Calculate the total work (w) and the total heat change (q) involved in the above processes.