(i) Ethylene glycol lowers the freezing point of water. It is called antifreeze solution.
(ii) 30% ethylene glycol solution means 30g of ethylene glycol in 100g of solution.
\({ \omega }_{ B }=30g,{ \omega }_{ A }=70g,{ K }_{ f }=1.86{ Km }^{ -1 },M_{ B }=62\)
\( { \triangle T }_{ f }=\frac { { K }_{ f }\times { \omega }_{ B }\times 1000 }{ { \omega }_{ A }\times { M }_{ B } } =\frac { 1.86\times 30\times 1000 }{ 70\times 62 } =12.86\)
The solution will freeze at\(-12.{ 86 }^{ \circ }C\) and therefore,it will be suitable.

(i) The cell walls of the vegetables have semi-permeable membrane. When the vegetables have dried, the concentration of water inside becomes low. When the dried or shrinked vegetables are placed in water, water enters into the cells due to osmosis. Hence, they swell and return to the original form.
(ii) The process is osmosis. It is defined as the flow of the solvent molecules from the solvent to the solution or from less concentrated solution to a more concentrated solution through a semi-permeable membrane.
(iii) The process will be accelerated with increase of temperature because osmosis becomes faster with increase of temperature.

(a) As a student of chemistry, we would prefer to buy the battery with cadmium plates, though it is costlier than the battery with lead plates. This is because
(i) Lead battery will result into harmful effects on human beings as well as on the environment because it causes environmental pollution.
(ii) A cadmium plated battery will have sustained long life benefit than short term gains with regard to health and money.
(b) Knowledge is useful only when put to practice; awareness of a lead-free petrol-legal aspect of pollution free environment. Less usage of lead batteries to keep ourselves and the environment healthy.

(a) Though D.D.T is a very powerful insecticide for mosquitoes, yet the excessive use of D.D.T has many problems. The use of D.D.T has the following disadvantages:
(i) Many species of insects develop resistance to D.D.T.
(ii) It has a high toxicity towards fish.
(iii) The chemical stability of D.D.T and its fat solubility has problems.
(iv) It is not biodegradable and its residues accumulate in environment and its long term effects could be dangerous.
(v) D.D.T is not metabolized very rapidly by animals rather it gets deposited and stored in fatty tissues. Because of its dangerous effects, its use has been banned in U.S.A in 1973. However, in spite of its dangerous effects, D.D.T is still being used in India because of non-availability of other cheaper insecticides.
(b) Mukesh's suggestion is very important to protect our environment. Because of long-term dangerous side effects of D.D.T., it should not be used to save our environment.

Since the volume of the gaseous products is less than that of the gaseous reactants, high pressure should favour the oxidation of sulphur dioxide. But a very high pressure may cause the corrosion of the vessel in which oxidation is carried. Therefore, a pressure of 2 to 3 bar is sufficient for the oxidation.