Covalent Character

Q.

The element which shows only negative oxidation state/s among following elements is:

1. Bromine

2. Chlorine

3. Fluorine

4. Iodine

Q. 6. The bond energy of B F bond in BF3 is 646 kJ/mol, while bond energy of N F bond in NF3 is 280 kJ/mol. This is because (1) N is more electronegative than B (2) Atomic mass of N is more than B (3) B F bond gets partial double bond character due to pp bond (4) N has a lone pair of electron while B does not

Q. Correct order of standard enthalpy of formation of diamond graphite, and fullerene is

1. ${\Delta }_f{H}_{\text{fullerene}}^{\circ }>{\Delta }_f{H}_{\text{diamond}}^{\circ }>{\Delta }_f{H}_{\text{graphite}}^{\circ }$
2. ${\Delta }_f{H}_{\text{diamond}}^{\circ }>{\Delta }_f{H}_{\text{graphite}}^{\circ }>{\Delta }_f{H}_{\text{fullerene}}^{\circ }$
3. ${\Delta }_f{H}_{\text{fullerene}}^{\circ }>{\Delta }_f{H}_{\text{graphite}}^{\circ }>{\Delta }_f{H}_{\text{diamond}}^{\circ }$
4. ${\Delta }_f{H}_{\text{graphite}}^{\circ }>{\Delta }_f{H}_{\text{diamond}}^{\circ }>{\Delta }_f{H}_{\text{fullerene}}^{\circ }$

Q.

Which of the following elements has greater tendency to show +2 oxidation state ?

1. Lead

2. Carbon

3. Silicon

4. Germanium

Q. If the bond energies of C-H , C≡C , O=O , C=O and O-H bonds are p , q , r , s , t respectively ( 1 ) [ 8s + 4t ] - [ 4p + q + 5r ] ( 2 ) [ 4p + 2q + 5r ] - [ 8s + 4t ] ( 3 ) [ 4p + 2q + 5r + 8s + 4t ] ( 4 ) [ 2p + q + 5r ] - [ 8s + 4t ]

Q.

what is the oxidation number of oxide.

Q.

Which M--M bond has highest bond energy -

1. Sn - Sn

2. Ge - Ge

3. Si - Si

4. Pb - Pb

Q.

Which of the following elements has greater tendency to show +2 oxidation state ?

1. Lead

2. Carbon

3. Silicon

4. Germanium

Q. When 0.4 mols of $A{l}_2{O}_3$ is heated with carbon, a brown solid X is formed along with evolution of a neutral gas which burns with blue flame.
What amount (in gm) of methane gas will be formed when X so formed is completely hydrolyzed with water?

Q. Ge(II) compounds are powerful reducing agents whereas Pb(IV) compounds are strong oxidants. It is because:

Q. What is the relation between bond length and bond strength?

Q. 11.37 Elements of group 14(a) exhibit oxidation state of +4 only(b) exhibit oxidation state of +2 and(q)(c) form M2 and M4+ ions+4(d) form M2+ and M4+ ions

Q. why is the bond enthalpy of 2 O-H bonds in water different

Q. Why do same elements like Hydrogen , oxygen have different oxidation number with different types of element ?

Q. Carbon and silicon belong to the ${14}^{th}$ group. The maximum coordination number of carbon in commonly occurring compounds is 4, whereas that of silicon is 6. This is due to:

1. the availability of low energy d-orbitals in silicon
   
2. large size of silicon
   
3. more electropositive nature of silicon
4. both (b) & (c)