Science (English Medium) Class 12 - CBSE Question Bank Solutions for Chemistry

Which of the following will have the maximum dipole moment?

Which among the following is the simplest sugar?

\[\ce{CH3-O-CH(CH3)2 + HI ->}\] Products is/are:

In lake test for Al³⁺ ions, there is the formation of coloured ‘floating lake’. It is due to ______.

Which one of the following are correctly arranged on the basis of the property indicated?

Read the passage given below and answer the following question:

The transition metals when exposed to oxygen at low and intermediate temperatures form thin, protective oxide films of up to some thousands of Angstroms in thickness. Transition metal oxides lie between the extremes of ionic and covalent binary compounds formed by elements from the left or right side of the periodic table. They range from metallic to semiconducting and deviate by both large and small degrees from stoichiometry. Since electron bonding levels are involved, the cations exist in various valence states and hence give rise to a large number of oxides. The crystal structures are often classified by considering a cubic or hexagonal close-packed lattice of one set of ions with the other set of ions filling the octahedral or tetrahedral interstices. The actual oxide structures, however, generally show departures from such regular arrays due in part to distortions caused by packing of ions of different size and to ligand field effects. These distortions depend not only on the number of d-electrons but also on the valence and the position of the transition metal in a period or group.

In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.

Assertion: Cations of transition elements occur in various valence states.

Reason: Large number of oxides of transition elements are possible.

Read the passage given below and answer the following question:

The transition metals when exposed to oxygen at low and intermediate temperatures form thin, protective oxide films of up to some thousands of Angstroms in thickness. Transition metal oxides lie between the extremes of ionic and covalent binary compounds formed by elements from the left or right side of the periodic table. They range from metallic to semiconducting and deviate by both large and small degrees from stoichiometry. Since electron bonding levels are involved, the cations exist in various valence states and hence give rise to a large number of oxides. The crystal structures are often classified by considering a cubic or hexagonal close-packed lattice of one set of ions with the other set of ions filling the octahedral or tetrahedral interstices. The actual oxide structures, however, generally show departures from such regular arrays due in part to distortions caused by packing of ions of different size and to ligand field effects. These distortions depend not only on the number of d-electrons but also on the valence and the position of the transition metal in a period or group.

In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.

Assertion: Crystal structure of oxides of transition metals often show defects.

Reason: Ligand field effect cause distortions in crystal structures.

Read the passage given below and answer the following question:

The transition metals when exposed to oxygen at low and intermediate temperatures form thin, protective oxide films of up to some thousands of Angstroms in thickness. Transition metal oxides lie between the extremes of ionic and covalent binary compounds formed by elements from the left or right side of the periodic table. They range from metallic to semiconducting and deviate by both large and small degrees from stoichiometry. Since electron bonding levels are involved, the cations exist in various valence states and hence give rise to a large number of oxides. The crystal structures are often classified by considering a cubic or hexagonal close-packed lattice of one set of ions with the other set of ions filling the octahedral or tetrahedral interstices. The actual oxide structures, however, generally show departures from such regular arrays due in part to distortions caused by packing of ions of different size and to ligand field effects. These distortions depend not only on the number of d-electrons but also on the valence and the position of the transition metal in a period or group.

In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.

Assertion: Transition metals form protective oxide films.

Reason: Oxides of transition metals are always stoichiometric.

The lattice site in a pure crystal cannot be occupied by ______.

A first order reaction is 50% completed in 1.26 × 10¹⁴ s. How much time would it take for 100% completion?

Which of the following graphs is correct for a first order reaction?

State a condition under which a bimolecular reaction is kinetically first order reaction.

With the help of an example explain what is meant by pseudo first order reaction.

Extent of physisorption of a gas increases with ______.

Which of the following is not a favourable condition for physical adsorption?

Physical adsorption of a gaseous species may change to chemical adsorption with ______.

In physisorption adsorbent does not show specificity for any particular gas because ______.

In which of the following reactions heterogenous catalysis is involved?

(a) \[\ce{2SO2 (g) + O2 (g) ->[NO(g)] 2SO3 (g)}\]

(b) \[\ce{2SO2 (g) ->[Pt(s)] 2SO3 (g)}\]

(c) \[\ce{N2 (g) + 3H2 (g) ->[Fe(s)] 2NH3 (g)}\]

(d) \[\ce{CH3COOCH3 (l) + H2O (l) ->[HCI(l)] CH3COOH (aq) + CH3OH (aq)}\]

Why is it important to have clean surface in surface studies?

Why is chemisorption referred to as activated adsorption?