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 

 Which among the following is a gas?

1. $B{F}_3$

2. $BC{l}_3$

3. $BB{r}_3$

4. $B{I}_3$

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. $A{l}_4{N}_6$

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

Aluminium deposited as vapours on glass forms a good mirror, essentially because:

(1) it has better shine than Ag

(2) it does not scratch

(3) coating is much smoother

(4) it does not tarnish in air

Conc. $HN{O}_3$ can be stored in a container of:

(1) Cu

(2) Al

(3) Zn

(4) Sn

Duralumin is an alloy of:

(1) Al and Mg

(2) Mg and Cu

(3) Al, Mg, Mn and Cu

(4) Al and Cu

Aluminium is not used:

(1) In thermite welding

(2) As oxidiser in metallurgy

(3) For making utensils

(4) In silvery paints