(a) Write balanced equations for the following reactions :
(i) Chlorine reacts with dry slacked lime.
(ii) Carbon reacts with concentrated `H_2SO_4`.
(b) Describe the contact process for the manufacture of sulphuric acid with special referecen to the reaction conditions, catalysts used and the yields in the process.

Explanation

(a) (i) `2Cl_2+2Ca(OH)_2 to CaCl_2+Ca(OCL_2)+2H_2O`
(ii) `C+2H_2SO_4to CO_2+2SO_22H_2O`
(b) In the contact process the sulphur dioxide is mixed with air and the mixture passed over a catalyst of vanadium (v) oxide `V_2O_5` at a relatively high temperature of about `450^@C` and at a pressure of between 1-2 atm. it is an exothermic oxidation .
`(1) 2SO_2(g)+O_2(g) hArr 2SO_3(g)" "(DeltaH=-196kJmol^(-))`
`K_(P)=(PSO_(3)^(2))/(PSO_(2)^(2)PO_2)`
(2) The sulphur trioxide is dissolved in concentrated sulphuric acid to form fuming sulphuric acid (oleum).
`SO_((3)(g))+H_2SO_((4)(l)) hArrH_2SO_((4)(l))`
(3) Water is then carefully added ot the oleum to produce concentrated sulphuric acid (`98%H_2SO_4`)
`H_2S_2O_(7(l))+H_2O_(l)hArr2H_2SO_(4(l)`
If the sulphur trioxide is added directly to water an acid mist from which is difficult to contain because the reaction to form sulphuric acid solution is very exothermic with a big K value.