Identify the false statement among the following about the halogens:
 

1. All form monobasic oxyacids(except HOF).
2. All are oxidizing agents.
3. All but fluorine show positive oxidation states.
4. Chlorine has the highest electron-gain enthalpy.

Which of the statements given below is incorrect?

1. $C{l}_2{O}_{7 }$is an anhydride of perchloric acid

2. $O_3$ molecule is bent

3. ONF is isoelectronic with $N{O}_2^{-}$

4. $O{F}_2$ is an oxide of fluorine

Roasting of sulphides gives the gas 'X' as a by-product. This is a colourless gas with the choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain. Its aqueous solution is acidic, acts as an oxidising agent, and its acid has never been isolated. The gas 'X' is:

1. SO₂

2. CO₂

3. SO₃

4. H₂S

Which of the following statements is not valid for oxoacids of phosphorus?

1. Orthophosphoric acid is used in the manufacture of triple  superphosphate

2. Hypoposhphorous acid is a diprotic acid

3. All oxoacids contain tetrahedral four coordinated phosphorus

4. All oxoacids contain at least one P=O unit and one P-OH group

Sulphur trioxide can be obtained by which of the following reaction

1. $CaS{O}_4+C\stackrel{∆}{\to }$

2. $F{e}_2(S{O}_4{)}_3\stackrel{∆}{\to }$

3. $S+H_{2}S{O}_4\stackrel{∆}{\to }$

4. $H_{2}S{O}_4+PC{l}_5\stackrel{∆}{\to }$

1.  1 sigma and 2 pi bonds

2.  2 sigma and 2 pi bonds

3.  1 sigma and 1 pi bonds

4.  2 sigma and 1 pi bonds

Which is the correct thermal stability order for ${\mathrm{H}}_2\mathrm{E}\left(\mathrm{E}=\mathrm{O}, \mathrm{S}, \mathrm{Se}, \mathrm{Te} \mathrm{and} \mathrm{Po}\right)?$

1.  ${\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Po}<{\mathrm{H}}_2\mathrm{O}<{\mathrm{H}}_2\mathrm{S}$

2.  ${\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{O}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Po}$

3.  ${\mathrm{H}}_2\mathrm{O}<{\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Po}$

4.  ${\mathrm{H}}_2\mathrm{Po}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{O}$