What are isomers? “Isomers of the first three members of alkane series are not possible”. Give a reason to justify this statement and draw structures of two isomers of butane, C₄H₁₀.

If you find coliform bacteria in a sample of water collected from a river, what would you conclude? Give a reason for such kind of water pollution.

Which natural resources are called the “biodiversity hot spots”? How these hot spots maintain ecological balance?

An organic compound ‘X’ is a liquid at room temperature. It is also a very good solvent and has the molecular formula C₂H₆O. on oxidation ‘X’ gives ‘Y’ which give, break effervescence on reacting with NaHCO₃. X reacts with Y in the presence of conc.H₂SO₄ to give another compound ‘Z’ which has a pleasant smell. Identify X, Y and Z. also write chemical equations to show the formation of Y and Z.

An element ‘A’ belongs to 3rd period and 17th group of the periodic table.

(a) Write atomic number and electronic configuration of ‘A’

(b) State whether A is a metal or a non – metal.

(c) Write the nature of bond formed if A reacts with another element B of electronic configuration 2, 8, 1.

(d) Write the chemical formula of the compound formed.