Board Paper of Class 12-Science 2022 Chemistry Term-II Delhi(Set 3) - Solutions

Account for the following:
(i) pk_b of aniline is more than that of methylamine.
(ii) Aniline does not undergo Friedel-Crafts reaction.
(iii) Primary amines have higher boiling points than tertiary amines.

OR

(i) Arrange the following compounds in the increasing order of their basic strength in aqueous solution:
CH₃ NH₂, (CH₃)₃ N, (CH₃)₂ NH
(ii) What is Hinsberg's reagent?
(iii) What is the role of pyridine in the acylation reaction of amines? VIEW SOLUTION

(a) Write the IUPAC name of the following complex: (b) On the basis of crystal field theory, write the electronic configuration of d⁵ ion if ∆₀ < P.
(c) What are ambidentate ligands? VIEW SOLUTION

(a) Write any two consequences of Lanthanoid Contraction.
(b) Name the element of 3d series which exhibits the largest number of oxidation states. Give reason. VIEW SOLUTION

Observe the graph shown in figure and answer the following questions :

(a) What is the order of the reaction ?
(b) What is the slope of the curve ?
(c) Write the relationship between k and $t_{\frac{1}{2}}$ (half life period) VIEW SOLUTION

Give reasons for the following statements:
(a) Transition elements and their compounds act as good catalysts.

(b) ${\mathrm{E}°}_{\left({\mathrm{Mn}}^{2+}/\mathrm{Mn}\right)}$ value is highly negative as compared to other elements.

(c) Cr²⁺ is a strong reducing agent. VIEW SOLUTION

(i) Define coagulation.
(ii) State Hardy-Schulze rule.
(iii) What is Electrophoresis?

OR

Write three differences between Physisorption and Chemisorption. VIEW SOLUTION

An aromatic compound 'A' (C₇H₆O₂) on reaction with aqueous ammonia and heating forms compound 'B'. 'B' on heating with Br₂ and alcoholic potash forms a compound 'C' of molecular formula C₆H₇N. Write the reactions involved and identify 'A', 'B', 'C'.

OR

A compound 'A' on reduction with iron scrap and hydrochloric acid gives compound 'B' with molecular formula C₆H₇N. Compound 'B' on reaction with CHCl₃ and alcoholic KOH produces an obnoxious smell of carbylamine due to the formation of 'C'. Identify 'A, 'B' and 'C and wrtie the chemical reactions involved. VIEW SOLUTION

Complete the following:

(i) CH₃CN $\underset{2. {\mathrm{H}}_2\mathrm{O}}{\overset{1. \mathrm{A}1\mathrm{H}{\left(\mathrm{i}-\mathrm{Bu}\right)}_2}{\to }}\text{'}\mathrm{A}\text{'}\underset{{\mathrm{H}}^{+}}{\overset{{\mathrm{H}}_2\mathrm{N}-\mathrm{OH}}{\to }}\text{'}\mathrm{B}\text{'}$

(ii) Write IUPAC name of the following compound:

            

(iii) Write chemical test to distinguish between the following compounds:
​Phenol and Benzoic acid

OR

Convert the following:
(i) Benzoic acid to Benzaldehyde
(ii) Propan-1- ol to 2-Bromopropanoic acid
(iii) Acetaldehyde to But-2-enal VIEW SOLUTION

Read the passage given below and answer the questions that follow:
Oxidation-reduction reactions are commonly known as redox reactions. They involve transfer of electrons from one species to another. In a spontaneous reaction, energy is released which can be used to do useful work. The reaction is split into two half reactions. Two different containers are used and a wire is used to drive the electrons from one side to the other and a Voltaic/Galvanic cell is created. It is an electrochemical cell that uses spontaneous redox reactions to generate electricity. A salt bridge also connects to the half cells. The reading of the voltmeter gives the cell voltage or cell potential or electromotive force. If ${\mathrm{E}}_{\mathrm{cell}}^{\mathrm{o}}$ is positive the reaction is spontaneous and if it is negative the reaction is non-spontaneous and is referred to as electrolytic cell. Electrolysis refers to the decomposition of a substance by an electric current. One mole of electric charge when passed through a cell will discharge half a mole of a divalent metal ion such as Cu²⁺. This was first formulated by Faraday in the form of laws of electrolysis.

The conductance of material is the property of materials due to which a material allows the flow of ions through itself and thus conducts electricity. Conductivity is represented by, k and it depends upon nature and concentration of electrolyte, temperature etc. A more common term molar conductivity of a solution at a given concentration is conductance of the volume of solution containing one mole of electrolyte kept between two electrodes with the unit area of cross-section and distance of unit length. Limiting molar conductivity of weak electrolytes cannot be obtained graphically.

(a) Is silver plate the anode or cathode?
(b) What will happen if the salt bridge is removed?
(c)When does electro-chemical cell behaves like an electrolytic cel1?
(d) (i) What will happen to the concentration of Zn²⁺ and Ag⁺ when E_cell = 0. (d) The molar conductivity of a 1.5 M solution of an electrolyte is found to be 138.9 S cm² mol^–1. Calculate the conductivity of this solution. VIEW SOLUTION