Orthoboric acid when heated to red hot gives-

1.	Metaboric acid	2.	Pyroboric acid
3.	Boron and water	4.	Boric anhydride

Borax is prepared by treating boric acid with:

(1) $NaN{O}_3$

(2) NaCl

(3) $N{a}_{2}C{O}_3$

(4) $NaHC{O}_3$

The main factor responsible for weak acidic nature of  B-F bonds in $B{F}_3$ is:

(1) large electronegativity of F

(2) three centred two electrons bonds in $B{F}_3$

(3) px-$d\mathrm{\pi }$ back bonding

(4) $p\mathrm{\pi }-\mathrm{p\pi }$ back bonding 

B-F bond order in $B{F}_3$ is:

(1) 1

(2) 2

(3) 3

(4) 4/3

Aluminium reacts with nitrogen to form:

1. AlN

2. $A{l}_2{N}_3$

3. $A{l}_{2}N$

4. $A{l}_4{N}_6$

Metal protected by a layer of its own oxide is:

(1) Al 

(2) Ag

(3) Au

(4) Cu

Which metal is powdered, suspended in oil and used as paint?

(1) Fe

(2) Sn

(3) Ag

(4) Al

Aluminium metal is corroded in coastal  places near to the sea, because protective oxide film:

(1) is removed by sea water

(2) reacts with sea water

(3) is attacked by salts present in sea water

(4) reacts with sand particles

The compound among the following that used in cosmetic surgery is:

1. Silica

2. Silicates

3. Silicones

4. Zeolites

Boric acid is polymeric because of:

1. Its acidic nature

2. Presence of hydrogen bonds

3. Its monobasic nature

4. Its geometry