Monday, August 24, 2009

IIT JEE Chemistry - Revision Set 2 - Past JEE Questions

1. The dipole moment of KCl is 3.336×10-29 Coulomb metre which indicates that it is a highly polar molecule. The interatomic distance between K+ and Cl- in this molecule is 2.6×10-10 m. Calculate the dipole moment of KCl molecule if there were opposite charges of one fundamental unit located at each nucleus. Calculate the percentage ionic character of KCl.

2. What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition, n =4 to n=2 of He+ spectrum?

3. The standard reduction potential for the half-cell,

NO3-(aq)+ 2H+(aq)+ e- → NO2(g) + H2O

is 0.78 V. Calcualte the reduction potential in 8 M H+.

4. Specify the products in this reaction

C6H5COOH + CH3MgI → ? + ?

5. Give the structure of A if A(C3H9N) reacts with benzenesulphonyl chloride to give a solid insoluble in alkali.

Source (1993 JEE paper)

Friday, August 21, 2009

Selected Past II JEE questions - Set 1 (for JEE 2010)

1. Give reasons - two or three sentences

a. Phenyl group is known to exert negative inductive effect. But each phenyl ring in biphenyl (C6H5-C6H5) is more reactive than benzene towards electrophilic substitution.

b. The species [CuCl4]2- exists while [CuI4]2- does not.

c. Bond dissociation energy of F2 is less than that of Cl2.

d. Hydrogen peroxide acts an an oxidising as well as a reducing agent.

e. Sulphur dioxide is a more powerful reducing agent in an alkaline medium than in acidic medium.

2. A light bluish green crystalline compound responds to the following tests:

i. Its acqueous solution gives a brown precipitate or coloration with alkaline K2[HgI4] solution.
ii. Its acqueous solution gives a blue colour with K3[Fe(CN)6] solution.
iii. Its solution in hydrochloric acid gives a white precipitate with BaCl2 solution.

Identify the ions present and suggest the formula of the compound.

3. Write tautomeric forms of phenol

4. At 27°C, hydrogen is leaked through a tiny hole into a vessel for 20 minutes. Another unknown gas at the same temperature and pressure as that of H2 is leaked through the same hole for 20 minutes. After the effusion of the gases the mixture exerts a pressure of 6 atmosphere. The hydrogen content of the mixture is 0.7 mole. If the volume of the container is 3 litres, what is the molar mass of the unknown gas.

5. An organic compound 'A' on treatment with ethyl alcohol gives a carboxylic acid 'B', and compound 'C'. Hydrolysis of 'C' under acidic conditions gives 'B' and 'D'. Oxidation of 'D' with KMnO4 also gives 'B'. 'B' on heating with Ca(OH)2 gives 'E' (molecular formula, C3H6O). 'E' does not give Tolleng test and does not reduce Fehling's solution but forms a 2, 4-dinitrophenylhydrazone. Identify 'A', 'B', 'C', 'D', and 'E'.