Sn crumbles to a powder in very cold weather, due to –

1. Expansion of the crystal lattice

2. Formation of SnO at low temperature

3. The conversion of Sn to powdery meta stannic acid

4. The transition from white tin to grey form, that is amorphous

Which of the following is responsible for the polymeric nature of boric acid?

1. Its acidic nature

2. Presence of hydrogen bonds

3. Its monobasic nature

4. Its geometry

Which of the following products is formed when orthoboric acid is heated to red heat?

Borax is prepared by treating boric acid with:

(1) $NaN{O}_3$

(2) NaCl

(3) $N{a}_{2}C{O}_3$

(4) $NaHC{O}_3$

Why is BF₃ a weaker Lewis acid than BCl₃?

1. High electronegativity of fluorine

2. Presence of three-center–two-electron bonds

3. pπ–dπ back-bonding

4. pπ–pπ 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