${}_{}$Why does BH₃ dimerise to form B₂H₆, whereas BCl₃ remains monomeric?

1. Greater electronegativity of chlorine than hydrogen

2. pπ–pπ back-bonding in BCl₃, which is absent in BH₃

3. Greater tendency of chlorine than hydrogen to form three-centre–two-electron bonds

4. Absence of vacant orbitals in BCl₃

Which of the following types of metals respond to the borax bead test?

1. Divalent metals

2. Heavy metals

3. Light metals

4. Metals that forms coloured metaborates

Why is CO₂ a gas at room temperature whereas SiO₂ is a solid?

1. Carbon dioxide is composed of discrete covalent ${\mathrm{CO}}_2$ molecules whereas silica has a continuous tetrahedral structure.

2. ${\mathrm{CO}}_2$ molecules are lighter than ${\mathrm{SiO}}_2$ molecules.

3. ${\mathrm{CO}}_2$ is more acidic than ${\mathrm{SiO}}_2$.

4. The melting point of silica is very high.

Which of the following shows bond in silicone?

1.  $\mathrm{Si}—\mathrm{C}—\mathrm{Si}—\mathrm{O}—\mathrm{Si}$

2.  $\mathrm{Si}—\mathrm{C}—\mathrm{Si}—\mathrm{C}—\mathrm{Si}$

3.  $—\stackrel{\mathbf{|}}{\mathrm{Si}}—\mathrm{O}—\stackrel{\mathbf{|}}{\mathrm{Si}}—\mathrm{O}—\stackrel{\mathbf{|}}{\mathrm{Si}}—$

4.  $\mathrm{Si}—\mathrm{Si}—\mathrm{Si}—\mathrm{Si}$

$\mathrm{CO}$ reacts with chlorine in presence of sunlight to give:

1.  ${\mathrm{COCl}}_2$

2.  ${\mathrm{CO}}_2$

3.  ${\mathrm{CCl}}_4$

4.  ${\mathrm{CHCl}}_3$

Butter of tin is:

1.  ${\mathrm{SnCl}}_2·5{\mathrm{H}}_2\mathrm{O}$

2.  ${\mathrm{SnCl}}_4·5{\mathrm{H}}_2\mathrm{O}$

3.  ${\mathrm{SnBr}}_2·2{\mathrm{H}}_2\mathrm{O}$

4.  ${\mathrm{SnBr}}_4·5{\mathrm{H}}_2\mathrm{O}$

Ordinary glass is:

1. Sodium silicate

2. Copper silicate

3. Calcium silicate

4. A mixture of calcium and sodium silicates with silica

The substance used to impart green colour to glass is:

1.  ${\mathrm{Cu}}_2\mathrm{O}$

2.  $\mathrm{CdS}$

3.  ${\mathrm{MnO}}_2$

4.  ${\mathrm{Cr}}_2{\mathrm{O}}_3$

Carbogen is:

1.  A mixture of ${\mathrm{O}}_2+5-10\%of\hspace{0.17em}{\mathrm{CO}}_2$.

2.  Used by pneumonia patients for respiration.

3.  Used by victims of $\mathrm{CO}$ for respiration.

4.  All of the above.

Death due to gunshot is caused by poisoning of:

1.  Hg

2.  Pb

3.  Fe

4.  As