Class XI Chemistry Chemical Bonding 5

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Question 1

The bond dissociation energy of B – F in BF₃ is 646 kJ mol^–1 whereas that of C – F in CF₄ is 515 kJ mol^–1. The correct reason for higher B-F bond dissociation energy as compared to that of C – F is:

• Asmaller size of B – atom as compared to that of C – atom
• Bstronger σ bond between B and F in BF₃ as compared to that between C and F in CF₄
• Csignificant pπ - pπ interaction between B and F in BF₃ whereas there is no pπ - pπ interaction between C and F.
• Dlower degree of pπ - pπ interaction between B and F in BF₃ than that between C and F in CF₄

Question 2

Lattice energy of BeCO₃ (I), MgCO₃ (II) and CaCO₃ (III) are in the order -

• AI > II > III
• BI < II < III
• CI < III < II
• DII < I < III

Question 3

Stability of the species Li₂, and increases in the order of

• A
• B
• C
• D

Question 4

Which of the following complex ions violates the EAN rule ?

• A[Fe(CO)₅]
• BNi(CO)₄
• C[Fe(CN)₆]^4–
• D[Mn(H₂O)₆]²⁺

Question 5

Which of the following statements regarding VI A group hydrides are correct

• AAll element of this group form volatile hydrides.
• BExcept H₂O all other hydrides are poisonous and have unpleasant odours.
• CThey are all very weak acids and there is an increase in acidic strength from H₂O to H₂Te.
• DAll of these.

Question 6

The maximum covalency for p-block elements is equal to -

• AThe number of unpaired p-electrons
• BThe number of paired d-electrons
• CThe number of unpaired s-and p-electrons
• DThe actual number of s-and p-electrons in the outermost shell

Question 7

Polarisation may be called as the distortion of the shape of an anion by an adjacently placed cation. Which of the following statements is/are correct?

• ALesser polarization is brought about by a cation of low radius
• BA large cation is likely to bring about a large degree of polarization
• CLarger polarisation is brought about by a cation of high charge
• DA small anion is likely to undergo a large degree of polarisation

Question 8

Out of following which one has maximum ionic character -

• ANaCl
• BKCl
• CCaCl₂
• DMgCl₂

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