A solid (A) reacts with strong aqueous NaOH, liberating a foul smelling gas (B), which spontaneously burns in the air, giving smoky rings. A and B are, respectively:

1. P₄ (red) and PH₃ 

2. P₄ (white) and PH₃

3. S₈ and H₂S

4. P₄ (white) and H₂S

The basic structural unit of silicates is-

Identify the correct statements among the following:

1. (a) and (c) only

2. (b) and (c) only

3. (c) and (d) only

4. (a), (b) and (c) only

Why does carbon show a much greater tendency for catenation than lead?

1. Due to the smaller size of C than that of Pb

2. Due to the smaller size of Pb than that of C

3. Due to the smaller ionization energy of C than that of Pb

4. Due to the inert pair effect

${\mathrm{}}_{}$
Which of the following correctly describes the acidic nature of H₃BO₃?

1. A Monobasic acid and a weak Lewis acid.

2. A Monobasic and a weak Bronsted acid..

3. A Monobasic and a strong Lewis acid.

4. A Tribasic and a weak Bronsted acid.

Which of the following orders is incorrect for the given properties of halogens?

The disproportionation reaction of ${\mathrm{H}}_3{\mathrm{PO}}_3$ is as follows:

${\mathrm{H}}_3{\mathrm{PO}}_3$ $\stackrel{∆}{\to }$ $\mathrm{X}$ $+$ $\mathrm{Y}$

 X and Y in the above reaction are:

1. H₃PO₂, HPO₂  

2. H₃PO₄, PH₃

3. H₂PO₆, PO₃

4. None of the above.

Which of the following is not a condition used in the Haber process for the manufacture of ammonia?

1. Pressure (around 200 ×10⁵ Pa)
2. Temperature (700 K)
3. Catalyst such as iron oxide.
4. Presence of inert gases.

Which of the following  hydrides has the lowest pKa value?

1. H₂O

2. H₂S

3. H₂Se

4. H₂Te