The B–F bond lengths in ${\mathrm{BF}}_3$ (130 pm) and $\mathrm{B}{{\mathrm{F}}_4}^{-}$(143 pm) differ because of-

1. Presence of triple bond character in ${\mathrm{BF}}_3$

2. Resonance in $\mathrm{B}{{\mathrm{F}}_4}^{-}$

3. Presence of a double bond character in ${\mathrm{BF}}_3$

4. Presence of a double bond character in $\mathrm{B}{{\mathrm{F}}_4}^{-}$

B–Cl bond has a dipole moment. Still, the BCl₃ molecule has zero dipole moment because-

1. The respective dipole-moments of the B–Cl bond add with each other

2. The respective dipole-moments of the B–Cl bond cancel each other

3. BCl₃ is tetrahedral in shape

4.  None of the above

CO is a poisonous gas because -

1. It forms a complex with hemoglobin.

2. The CO–Hb complex is about 300 times more stable than the $O_2$–Hb complex.

3. It can kill a person through suffocation on not receiving oxygen.

4. All of the above

An excessive content of CO₂ is responsible for global warming as-

1. Higher the level of carbon dioxide, higher is the amount of heat trapped.

2. Higher the level of oxygen, higher is the amount of heat trapped.

3. Higher the level of carbon dioxide, lesser is the amount of heat trapped.

4. Higher the level of oxygen, lesser is the amount of heat trapped.

The sharp decrease in ionization enthalpy from carbon to silicon happens because of-

1.  Decrease in the charge of elements upon moving down the group.

2.  Decrease in the atomic sizes of elements upon moving down the group.

3.  Increase in the atomic sizes of elements upon moving down the group.

4.  Increase in the charge of elements upon moving down the group.

The correct explanation for the lower atomic radius of Ga as compared to Al is -

1. Poor shielding effect of the 2d-electrons

2. Poor shielding effect of the 3d-electrons

3. Poor shielding effect of the 3p-electrons

4. Poor shielding effect of the 2s-electrons

Amphoteric oxides are:

1. ${\mathrm{Tl}}_2{\mathrm{O}}_3$, ${\mathrm{SiO}}_2$

2. ${\mathrm{CO}}_2$, ${\mathrm{B}}_2{\mathrm{O}}_3$

3. ${\mathrm{B}}_2{\mathrm{O}}_3$, ${\mathrm{SiO}}_2$

4. ${\mathrm{AI}}_2{\mathrm{O}}_3$, ${\mathrm{PbO}}_2$

When a metal X is treated with sodium hydroxide, a white precipitate (A) is obtained, which is soluble in excess of NaOH to give soluble complex (B). Compound (A) is soluble in dilute HCl and forms compound (C). The compound (A) when heated strongly gives (D), which is used to extract the metal.

X, C & D are respectively - 

1. Aluminium, aluminium chloride, alumina

2. Aluminium, aluminium hydroxide, aluminium chloride

3. Aluminium hydroxide, aluminium chloride, aluminium

4. Aluminium hydroxide, aluminium chloride, sodium tetrahydroxoaluminate

An aqueous solution of Borax is-

1. Neutral

2. Amphoteric

3. Basic

4. Acidic

Boric acid is polymeric due to-

1. Its acidic nature.

2. The presence of hydrogen bonds.

3. Its monobasic nature.

4. Its geometry.