Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Chemistry

Although +3 is the characteristic oxidation state for lanthanoids but cerium also shows +4 oxidation state because:

(i) it has variable ionisation enthalpy

(ii) it has a tendency to attain noble gas configuration

(iii) it has a tendency to attain f 0 configuration

(iv) it resembles Pb⁴⁺ 

Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why?

Although +3 oxidation states is the characteristic oxidation state of lanthanoids but cerium shows +4 oxidation state also. Why?

Match the compounds/elements given in Column I with uses given in Column II.

Match the statements given in Column I with the oxidation states given in Column II.

Match the property given in Column I with the element given in Column II.

On the basis of Lanthanoid contraction, explain the following:

Nature of bonding in \[\ce{La2O3}\] and \[\ce{Lu2O3}\] .

On the basis of Lanthanoid contraction, explain the following:

Trends in the stability of oxo salts of lanthanoids from \[\ce{La}\] to \[\ce{Lu}\].

On the basis of Lanthanoid contraction, explain the following:

Stability of the complexes of lanthanoids.

On the basis of Lanthanoid contraction, explain the following:

Radii of 4d and 5d block elements.

On the basis of Lanthanoid contraction, explain the following:

Trends in acidic character of lanthanoid oxides.

Which of the following reactions will yield phenol?

(i)
(ii)
(iii)
(iv)

Name the starting material used in the industrial preparation of phenol.

Name the electrophile produced in the reaction of benzene with benzoyl chloride in the presence of anhydrous \[\ce{AlCl3}\]. Name the reaction also.

Ethylbenzene is generally prepared by acetylation of benzene followed by reduction and not by direct alkylation. Think of a possible reason.

Can Gatterman-Koch reaction be considered similar to Friedel Craft’s acylation? Discuss.

Match the common names given in Column I with the IUPAC names given in Column II.

Match the acids given in Column I with their correct IUPAC names given in Column II.

Match the example given in Column I with the name of the reaction in Column II.

	Column I (Example)		Column II (Reaction)
(i)	\[\begin{array}{cc} \phantom{...}\ce{O}\phantom{..............................}\ce{O}\phantom{}\\ \phantom{...}||\phantom{..............................}||\phantom{}\\ \ce{CH3 - C - Cl + H2 ->[Pd - C/BasO4] CH3 - C - H} \end{array}\]	(a)	Friedel Crafts acylation
(ii)		(b)	HVZ reaction
(iii)		(c)	Aldol condensation
(iv)	\[\begin{array}{cc} \ce{R - CH2 - COOH ->[Br/Red P] R - CH - COOH}\\ \phantom{.....................}|\\ \phantom{.......................}\ce{Br} \end{array}\]	(d)	Cannizaro’s reaction
(v)	\[\ce{CH3 - CN ->[(i) SnCl2/HCl][(ii) H2O/H+] CH3CHO}\]	(e)	Rosenmund’s reductio
(vi)	\[\ce{2CH3CHO ->[NaOH] CH3 - CH = CHCHO}\]	(f)	Stephen’s reaction

An alkene ‘A’ (Mol. formula \[\ce{C5H10}\]) on ozonolysis gives a mixture of two compounds ‘B’ and ‘C’. Compound ‘B’ gives positive Fehling’s test and also forms iodoform on treatment with \[\ce{I2}\] and \[\ce{NaOH}\]. Compound ‘C’ does not give Fehling’s test but forms iodoform. Identify the compounds A, B and C. Write the reaction for ozonolysis and formation of iodoform from B and C.