Vapour pressures of benzene and toluene in a mixture at 50^oC are given in mm by P = 179 X_B + 92 where X_B is the mole fraction of benzene. Calculate
(a) Vapour pressures of pure benzene and toluene at 50^oC.
(b) Vapour pressure of a liquid mixture obtained by mixing 224 g benzene and 184 g of toluene.
(c) If the vapours are removed and condensed into liquid and again brought to the temperature of 50^oC, what would be the mole fraction of benzene in the vapour phase ?

Three electrolytic cells A, B, C containing solutions of ZnSO₄, AgNO_3, and CuSO₄, respectively are connected in series. A steady current of 1.5 amperes was passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow? What mass of copper and zinc were deposited?

(a) Complete the following chemical equations:
(i) \(\underset{Hot\ and\ conc.}{NaOH(aq)}\) + Cl₂(g) \(\longrightarrow \)
(ii) XeF₆(s) + H₂O(l) \(\longrightarrow \)
(b) How would you account for the following?
(i) The value of electron gain enthalpy with negative sign for sulphur is higher than that for oxygen.
(ii) NF₃ is an exothermic compound but NCl₃ is endothermic compound.
(iii) ClF₃ molecule has a T-shaped structure and nota trigonal planar one.

(a) Alkyl halides are amongst the most reactive of the organic compounds. why ?

(b) The treatement of alkyl halides with alcoholic KOH leads to the formation of alkenes. Justify.

Account for the following:
(i)\({ CH }_{ 3 }CHO\)  is more reactive than towards\(​​{ CH }_{ 3 }CO{ CH }_{ 3 }\) reaction with HCN.
(ii) Carboxylix acid is a stronger acid than phenol

Write the structures of fragments produced on complete hydrolysis of DNA. How are they linked in DNA molecule ? Draw a diagram to show pairing of nuclotide bases in double helix of DNA.

What are food additives ? Discuss briefly the various types of food additives citing at least one example.

Two first reactions proceed at the same rate at 15^oC when started with same initial concentration. The temperature coefficient of the first reaction is 2 while that of the second reaction is 3. What will be the ratio of the rates of these reactions at 55^oC ?