Boric acid on heating at $150°\mathrm{C}$ gives:

1. ${\mathrm{B}}_2{\mathrm{O}}_3$

2. ${\mathrm{H}}_2{\mathrm{B}}_4{\mathrm{O}}_7$

3. ${\mathrm{HBO}}_2$

4. ${\mathrm{H}}_2{\mathrm{BO}}_3$

Orthoboric acid when heated to red hot gives-

 Which among the following is a gas?

1. $B{F}_3$

2. $BC{l}_3$

3. $BB{r}_3$

4. $B{I}_3$

What happens when aluminium is added to an aqueous potassium hydroxide solution?

1. No reaction takes place 

2. Oxygen gas is evolved

3. Water is produced 

4. Hydrogen gas is evolved

CO₂ and N₂ are non-supporters of combustion. However, for putting out fires CO₂ is preferred over N₂ because CO₂:

1. Does not burn.

2. Forms non-combustible products with burning substances.

3. Is denser than nitrogen.

4. Is a more reactive gas.

Quartz is made of silicon and oxygen joined in a network arrangement that is similar to:

1. Diamond

2. Graphite

3. $O_2$

4. None of the above

When ${\mathrm{SnCl}}_2$ reacts with ${\mathrm{HgCl}}_2$, the product formed is:

1. $\mathrm{Sn}+{\mathrm{HgCl}}_4$

2. $\mathrm{Sn}+{\mathrm{Cl}}_2+{\mathrm{Hg}}_2{\mathrm{Cl}}_2$

3. ${\mathrm{SnCl}}_4<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{Hg}}_2{\mathrm{Cl}}_2$

4. None of the above

The soldiers of the Napolean army while at the Alps during freezing winter suffered a serious problem with regards to the tin buttons of their uniforms. White Metallic tin buttons get converted to grey powder. This transformation is related to-

1. An interaction with water vapour contained in humid air

2. A change in the crystalline structure of tin

3. A change in the partial pressure of $O_2$ in the air

4. An interaction with $N_2$ of air at low temperature

The amphoteric oxide among the following is :

Aluminium chloride in acidified aqueous solution forms a complex 'A'.
The formula of A and hybridisation state of Al in 'A' is respectively:

1. [Al(H₂O)₆]³⁺, sp³d²

2. [Al(H₂O)₄]³⁺, sp³

3. [Al(H2O)4]3+, dsp2

4. [Al(H₂O)]³⁺, d²sp³