Explain the vulcanisation of rubber.

Vulcanisation is the process of heating natural or raw rubber with sulphur with an appropriate additive at a temperature range between 373 - 415 K to improve its physical properties. Sulphur forms cross-links at the reactive sites of the double bond and thus, rubber gets stiffened, i.e. becomes less sticky and plastic, more resistant to swelling by organic liquids and with enhanced elasticity, higher water absorption capacity and higher tensile strength. The diagram below depicts the vulcanized rubber whose polymer chains are held with disulphide bonds.

Name the monomers present in the following polymer- PVC

PVC stands for polyvinyl chloride is a thermoplastic. It is commercially important polymer manufactured by the addition polymerization or chain growth polymerization of vinyl chloride CH 2 = CH - Cl or chloroethene, which is the monomer of PVC. Therefore, the following reaction is observed- Note- Monomers used in vinyl polymerization should be highly pure organic compounds since traces of impurities can interfere during polymerization.

What is the effect on ∆ H and ∆ S during the process of adsorption?

During the process of adsorption, ∆ H becomes negative and ∆ S becomes positive which results in decrease of ∆ G i.e, with negative sign. This is because adsorption is an exothermic and spontaneous process and randomness or disorder decreases during adsorption. Therefore, we can conclude- ∆ G = ∆ H - T ∆ S ∆ G = ‐ ve - ‐ ve ∆ G = ‐ ve

Write the expression for Freundlich adsorption isotherm.

Freundlich adsorption isotherm is a curve that expresses the variation in the amount of gas adsorbed by the adsorbent with the temperature at constant pressure. x m = k . p 1 n ( n > 1 ) , ‘ k ’ and ‘ n ’ are constants that depend on the nature of the adsorbent and the gas at a particular temperature. Fig. shows the graph of x m vs P

What is peptization? Give an example.

The process which involves the conversion of freshly prepared precipitate into a colloidal solution by adding any suitable electrolyte is called peptization. The electrolyte added into the precipitate is called peptizing agent or the dispersion agent. It occurs due to the adsorption of one of the ions of the electrolyte which then gives the colloidal particle a positive or a negative charge that is in accordance with the charge of the adsorbed ion. For example: If freshly prepared ferric hydroxide is treated with a small quantity of FeCl 3 (electrolyte) solution, a dark reddish-brown colloidal solution Fe ( OH ) 3 is obtained. Here FeCl 3 is peptizing agent.

Give two examples for heterogeneous catalysis.

Oxidation of sulphur dioxide Into sulphur trioxide In the presence of Pt . 2 SO 2 g → Pt s 2 SO 3 g The reactant Is In the gaseous state while the catalyst Pt Is In the solid state. Combination between dinitrogen and dihydrogen to form ammonia In the presence of finely divided Iron In Haber’s process. N 2 g + 3 H 2 g → Fe s 2 NH 3 g

Give an expression for Freundlich adsorptioin isotherm.

Given an expression at low pressure, the variation in adsorption ( x / m ) with pressure P at a particular temperature is: x m ∝ p Or x m = Kp . Where K is constant. The expression represent Freundlich adsorption isotherm.

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Among physisorption or chemisorption which one has higher enthalpy of adsorption?

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