Chemistry-2000 Set III

Q.1 Define the term denaturation in relation of protein.
Ans1. Disruption of native conformation of a protein due to change in pH, temperature, salts and the likes, is called denaturation.

Q.2 What are the properties of
(i) Ferromagnetics and
(ii) ferroelectrics? Give an example of each type.

Ans2. Ferromagnetic substance are those which show attraction towards external magnetic field and show a permanent magnetism even when the magnetic field is removed. In such substance large number of unpaired electrons aligned in same direction are present.
Example : Fe
Ferroelectric solids are those piezoelectric solids in which permanent dipole present are spontaneously polarised even in the absence of electric field and the direction of polarisation can be changed by applying an electric field.
Example : Barium Titanate (BaTiO3), Rochelle salt.

Q.3 (a) How and where is carbon-14 produced in nature and how it is incorporated into living plant?
(b) Write the principle of radiocarbon dating.

Ans3. (i) Radioactive isotopes carbon-14 is formed by the bombardment of nitrogen in the upper atmosphere by cosmic rays :
147 N + 10 n ——-> 146 C + 11H
The C-14 produced is eventually incorporated into the carbondioxide of air which in turn is incorporated into living plants by the process of photosynthesis and then finds its way into the animal which eats plant.
(ii) The principle of the radiocarbon dating is based on the fact that living matter contains a definite proportion of the radioactive C-14. Once the plant or animal dies, the process of incorporation of carbon stops. And already present ready to decay.
146 C —-> 147 N + O-1e; t1/2 = 5770 years
By knowing the equilibrium concentration of C-14 in a living plant and the concentration of C-14 in a dead piece of organic matter at a particular time, the age of the material can be determined.

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