Compound of sulphur that has $-\mathrm{O}-\mathrm{O}-$linkage among the following is:

1. ${\mathrm{H}}_2{\mathrm{SO}}_4,$ $\mathrm{sulphuric}$ $\mathrm{acid}$

2. ${\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_8,$ $\mathrm{peroxodisulphuric}$ $\mathrm{acid}$

3. ${\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_7,$ $\mathrm{pyrosulphuric}$ $\mathrm{acid}$

4. ${\mathrm{H}}_2{\mathrm{SO}}_3,$ $\mathrm{sulphurous}$ $\mathrm{acid}$

The correct thermal stability order for \(\mathrm{{H}_2 {E}},\)  \(\mathrm{{ E}= {O}, {S}, {Se}, {Te}} \text { and } \mathrm{Po}\)  among the following is:
1. \(\mathrm{{H}_2 {Se}<{H}_2 {Te}<{H}_2 {Po}<{H}_2 {O}<{H}_2 S}\)
2. \(\mathrm{{H}_2 {~S}<{H}_2 {O}<{H}_2 {Se}<{H}_2 {Te}<{H}_2 {Po}}\)
3. \(\mathrm{{H}_2 {O}<{H}_2 {~S}<{H}_2 {Se}<{H}_2 {Te}<{H}_2 {PO}}\)
4. \(\mathrm{{H}_2 {Po}<{H}_2 {Te}<{H}_2 {Se}<{H}_2 {~S}<{H}_2 {O}}\)

Identify the correct formula of 'oleum' from the following

1. H₂S₂O₇

2. H₂SO₃

3. H₂SO₄

4. H₂S₂O₈

Which of the following reactions does not exhibit the oxidising behaviour of H₂SO₄?

1. Cu + 2H₂SO₄ → CuSO₄ + SO₂ + 2H₂O

2. 3S + 2H₂SO₄ → 3SO₂ + 2H₂O

3. C + 2H₂SO₄ → CO₂ + 2SO₂ + 2H₂O

4. CaF₂ + H₂SO₄ → CaSO₄ + 2HF

Which of the statements given below is incorrect?

1. \(\mathrm{C l_{2} O_{7  }}\)${}_{}$is an anhydride of perchloric acid
2. \(\mathrm{O_{3}}\)${\mathrm{}}_{}$ molecule is bent
3. ONF is isoelectronic with \(\mathrm{N O_{2}^{-}}\)${}_{}^{}$ 
4. \(\mathrm{O F_{2}}\) is an oxide of fluorine

The acidity of diprotic acids in aqueous solution increases in the order:

1. H₂S < H₂Se < H₂Te

2. H₂Se < H₂S < H₂Te

3. H₂Te < H₂S < H₂Se

4. H₂Se < H₂Te < H₂S