Science (English Medium) Class 11 - CBSE Question Bank Solutions for Chemistry

Why does presence of a nitro group make the benzene ring less reactive in comparison to the unsubstituted benzene ring. Explain.

Assertion (A): Nitration of benzene with nitric acid requires the use of concentrated sulphuric acid.

Reason (R): The mixture of concentrated sulphuric acid and concentrated nitric acid produces the electrophile, \[\ce{NO^{+}2}\].

Use molecular orbital theory to explain why the Be₂ molecule does not exist.

Differentiate between the principle of estimation of nitrogen in an organic compound by Dumas method.

Differentiate between the principle of estimation of nitrogen in an organic compound by Kjeldahl’s method.

A sample of 0.50 g of an organic compound was treated according to Kjeldahl’s method. The ammonia evolved was absorbed in 50 mL of 0.5 M H₂SO₄. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation. Find the percentage composition of nitrogen in the compound.

The first ionization constant of H_2­­S is 9.1 × 10^–8. Calculate the concentration of HS^–ion in its 0.1 M solution. How will this concentration be affected if the solution is 0.1 M in HCl also? If the second dissociation constant of H₂S is 1.2 × 10^–13, calculate the concentration of S^2– under both conditions.

Stable form of C may be represented by the formula:

The molecular formula of the compound formed from \[\ce{B}\] and \[\ce{C}\] will be ______.

The electronic configuration of the outer most shell of the most electronegative element is ______.

Amongst the following elements whose electronic configurations are given below, the one having the highest ionisation enthalpy is ______.

Dimagnetic species are those which contain no unpaired electrons. Which among the following are dimagnetic?

(i) \[\ce{N2}\]

(ii) \[\ce{N^{2-}2}\]

(iii) \[\ce{O2}\] 

(iv) \[\ce{O^{2-}2}\]

Explain the shape of \[\ce{BrF5}\].

Explain why \[\ce{PCl5}\] is trigonal bipyramidal whereas \[\ce{IF5}\] is square pyramidal.

Which of the following statements is correct?

In DNA and RNA, nitrogen atom is present in the ring system. Can Kjeldahl method be used for the estimation of nitrogen present in these? Give reasons.

Match Column I with Column II.

Which of the following reactions of methane is incomplete combustion:

The intermediate carbocation formed in the reactions of HI, HBr and HCl with propene is the same and the bond energy of HCl, HBr and HI is 430.5 kJ mol^–1, 363.7 kJ mol^–1 and 296.8 kJ mol^–1 respectively. What will be the order of reactivity of these halogen acids?

Predict the major product (s) of the following reactions and explain their formation.

\[\ce{H3C - CH = CH2 ->[(Ph.CO.O)2][HBr]}\]

\[\ce{H3C - CH = CH2 ->[HBr]}\]