p-Dichlorobenzene has higher m.p. and lower solubility than those of o- and m-isomers. Discuss.

Explain the following: Primary amines have higher b.p. than ter-tiary amines

Calculate the number of moles in 1m^3 of gas at N. T. P

The critical temperature of water is higher than that of O_2 because the H_2O molecule has

The sum of first n terms of an A.P. is m and that of first m terms is n. Prove that the sum of first m + n terms is -(m + n) .

Non-Stoichiometric cuprous oxide, Cu_2O can be prepared in laboratory. In this oxide, copper to oxygen ratio is slightly less than 2:1. Can you account for the fact that this substance is a p-type semiconductor?

P and Q are respectively the base and the vertex of the tower PQ.AB is another tower which is at a certain distance apart from PQ.The height of AB is less than that of PQ and the base of AB is A.The angles of elevation of Q from A and B are respectively 60^@ and 45^@ .If AB=40m,find PQ,QA and QB.

In a G.P., the (p + q)th term is m and (p-q)th term is n. Find its pth term.

A body of mass m is moved to a height to equal to the radius of earth.The increase in P.E is

PA and PB are two tangents drawn from an external point P at the points A and B on a circle with centre O.If another tangent to the circle intersects PA and PB at L and M respectively,show that LM=AL+BM.