1. For a solution of 3.795 g sulphur in 100 g CS2,the boiling point was 319.81 K. For pure CS2,
the boiling point is 319.45 K and the enthalpy of vaporization is 351.87 Jg-1. What is the molar
mass and formula’ofsu1jhur in CS2?
2. The solubility products of Pbl2 is .7.50 x 1O-9 at15°C and 1.58 x 10-8 at 25°C. Calculate solubility
in g/L at 75°C?
3. Iron Crystallizes indifferent modifications. At about 910°C the body cent red cubic form undergoes transition to the face centered cubic y form. Assuming that ‘the distance between the nearest neighbours is same in the two forms at transition temperature, calculate the ratio of the density of iron to that of a iron at that temperature.
4. The wavelength of light evolved associated with an electron Jump from the 5th orbit of Bohr hydrogen atom to the 3rd orbit is 1.28 x104 A0. What will be the wavelength of light emitted when the same electron 3rd orbit jumps to the 2nd orbital?
5. Convert using
with aldol condensation as key step.
6. In solid ammonia, each NH3 molecule has six other NH3 molecules as nearest neighbours.ΔH of sublimation of NH3’at the melting point is 30.8 kJ/mole, and the estimated H of sublimation in the absence of hydrogen bonding is 14.4 kJ/mol. What is the strength of hydrogen bond in solid ammonia?
7. A 0.1 m solution of NaCIO3 freezes at -0.3433°C. What would you predict for the boiling point of this aqueous solution at 1 atm pressure? At 0;001 m concentration of this same salt, the electrical interferences between the ions no longer exist, because the ions are, on an average, too far apart from each other Predict the freezing point of this more dilute solution (Kffor water = 1.86 K kg mol-1 and Kb for water = 0.513 K kg mol-1).
8. An aromatic ketone (X) has the M.F. C10H12 O2 on vigorous oxidation, it gives (Y), dibasic acid (C9H8O5) which easily gives an anhydride on heating. The ketone (K) gives (Z) (C9H10O3), a monobasic acid on heating with bromine and NaOH. (Z) on decarboxylation with soda lime gives 3-methyl anisole. Determine (X), (Y) and (Z).
9. Bring about following one step transformations:
10. Two isomeric compounds (A) and (B) on analysis give 45.85% C, 8.91 % hydrogen. Further sodium extract of 1.0 g of the compound gives 1.83 g of AgC1 with acidified AgNO3 solution Chlorination of (A) with Cl2 and light gave two dichloro derivatives while (B) gave three different dichloro compounds. What are (A) and (B) and also give the structural formulae of the dichloride’s obtained, from each.
SOLUTIONS
3. For γ form there are 4 atoms per unit cell and edge length
For α form there are 2 atoms per unit cell and edge length
Density of form
Density of form
Dividing 1 by 2, we get 1.089 1.09 the ratio of their densities.
6. Total strength of all hydrogen bonds
= 30.8— 14.4 = 16.4 kJ/mol.
There are 6 nearest neighbours, but each hydrogen bond involves 2 ammonia molecules.
Strength of each H-bond in solid NH3
7.
On chlorination in presence of light compound (A) gives two dichloro derivatives while (B) gives
three dichloro derivatives.
A must be iso-propyl chloride:
B is n-propyl chloride: