Chemistry 12 Chapter 8 Exemplar Solutions the P and F Block Elements Part 9

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Question 68:

(a) Answer the following questions:

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

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

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

(b) Identify the metal and justify your answer.

(i) Carbonyl

(ii)

Answer:

(a)

(i) , because the electronic configuration of is . So second electron needs to beremoved from completely filled d-orbital.

(ii) [Hint: As above]

(iii) Zn [Hint: No unpaired electron for metallic bonding]

(b)

(i) [Hint: EAN rule]

(ii) [Hint: shows oxidation state; d-electrons are not involved in bonding.]

Question 69:

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

Answer:

Interstitial compounds. Characteristic properties:

(i) High melting points, higher than those of pure metals.

(ii) Very hard.

(iii) Retain metallic conductivity.

(iv) Chemically inert.

Question 70:

(a) Transition metals can act as catalysts because these can change their oxidation state. How does catalyse the reaction between iodide and persulphate ions?

(b) Mention any three processes where transition metals act as catalysts.

Answer:

(a) Reaction between iodide and persulphate ions is:

Role of :

(b)

(i) Vanadium (V) oxide in contact process for oxidation of to .

(ii) Finely divided iron in Haber’s process in conversion of and to .

(iii) in preparation of oxygen from .

Question 71:

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 in the presence of potassium nitrate to give compound (B). On heating compound (C) with conc. and , 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.

Answer:

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