(a) Give any two differences between lyophilic and lyophobic colloids.
(b) Write the two steps involved in the mechanism of enzyme catalysed reaction.
(c) What is the entropy change `(Delta s)` for adsorption ?

Explanation

(a)
(b) Mchanism of enzyme catalysis: A number of cavities of characteristic shape with active group `( -NH_(2), -COOH, -SH, -OH, etc)` are present on the surface of colloidal particles of enzymes. Reactant molecules of specific shape fit into these cavities to from actived complex, which further decomposes to yield products. Mainly two stens are involved in this entire process.
This mechanism involves only one step.
The nucleophile `OH`-attack from the rear side of the leaving group. A transition state with partial formation of `C- OH` bond and partial breaking of C-Br bond takes place simultaneously.
The rate of the reaction depends both on the concentration of nucleophile as well as alkyl halide. Hence, it is a second order reaction. In `S_(N)2` reaction complete inversion of configuration takes place.
Binding of enzyme to substrate (reactant) to from activated complex.
`E+S to ES^(**)`
(c) Decreases.