Science (English Medium) इयत्ता १२ - CBSE Question Bank Solutions

Assertion: Separation of \[\ce{Zr}\] and \[\ce{Hf}\] is difficult.

Reason: Because \[\ce{Zr}\] and \[\ce{Hf}\] lie in the same group of the periodic table.

Assertion (A): Cu cannot liberate hydrogen from acids.

Reason (R): Because it has positive electrode potential.

Assertion: The highest oxidation state of osmium is +8.

Reason: Osmium is a 5d-block element.

Identify A to E and also explain the reactions involved.

When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallised from the solution. When compound (C) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.

When an oxide of manganese (A) is fused with KOH in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (B). Compound (B) disproportionates in neutral or acidic solution to give purple compound (C). An alkaline solution of compound (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.

Answer the following question:

Which element of the first transition series has highest second ionisation enthalpy?

Answer the following question:

Which element of the first transition series has highest third ionisation enthalpy?

Answer the following question:

Which element of the first transition series has lowest enthalpy of atomisation?

Identify the metal and justify your answer.

Carbonyl \[\ce{M(CO)5}\]

Identify the metal and justify your answer.

\[\ce{MO3F}\]

Mention the type of compounds formed when small atoms like H, C and N get trapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.

Transition metals can act as catalysts because these can change their oxidation state. How does \[\ce{Fe(III)}\] catalyse the reaction between iodide and persulphate ions?

Mention any three processes where transition metals act as catalysts.

A violet compound of manganese (A) decomposes on heating to liberate oxygen and compounds (B) and (C) of manganese are formed. Compound (C) reacts with KOH in the presence of potassium nitrate to give compound (B). On heating compound (C) with conc. \[\ce{H2SO4}\] and \[\ce{NaCl}\], chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.

Write a test to detect the presence of double bond in a molecule.

Discuss the nature of C – X bond in the haloarenes.

Assertion: Nitration of chlorobenzene leads to the formation of m-nitrochlorobenzene.

Reason: –NO₂ group is a m-directing group.

What is the structure and IUPAC name of glycerol?

When phenol is treated with bromine water, white precipitate is obtained. Give the structure and the name of the compound formed.