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

Conjugate acid of a weak base is always stronger. What will be the decreasing order of basic strength of the following conjugate bases?

\[\ce{OH-, RO-, CH3COO-, Cl-}\]

\[\ce{pH}\] of 0.08 mol dm^–3 \[\ce{HOCl}\] solution is 2.85. Calculate its ionisation constant

Assertion (A): Aqueous solution of ammonium carbonate is basic.

Reason (R): Acidic/basic nature of a salt solution of a salt of weak acid and weak base depends on K_a and K_b value of the acid and the base forming it.

For an electrophilic substitution reaction, the presence of a halogen atom in the benzene ring:

(i) deactivates the ring by inductive effect

(ii) deactivates the ring by resonance

(iii) increases the charge density at ortho and para position relative to meta position by resonance

(iv) directs the incoming electrophile to meta position by increasing the charge density relative to ortho and para position.

In an electrophilic substitution reaction of nitrobenzene, the presence of nitro group:

(i) Deactivates the ring by inductive effect.

(ii) Activates the ring by inductive effect.

(iii) Decreases the charge density at ortho and para position of the ring relative to meta position by resonance.

(iv) Increases the charge density at meta position relative to the ortho and para positions of the ring by resonance.

Why do alkenes prefer to undergo electrophilic addition reaction while arenes prefer electrophilic substitution reactions? Explain.

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.