The oxidation states of the S atom in $S_4{O}_6^{2-}$  from left to right, respectively, are:

1. + 6, 0, 0, and +6                         

2. +5, +1, +1, and +5

3. +5, 0, 0, and +5                           

4. +3, +1, +1, and +3

One gas bleaches the coloured matter by reduction temporary while the other one by oxidation
permanently. The gases are respectively:

(1) $S{O}_2 and C{l}_2$                             

(2) $O_3 and C{l}_2$

(3) $H_{2}S and C{O}_2$                             

(4) $C{l}_2 and S{O}_2$

$H_{2}S{O}_4$  cannot be used to prepare HI from KI as:

(1) Its reaction with KI is very slow.                   

(2) It oxidizes HI to iodine.

(3) It disproportionates HI.                               

(4) It reduces HI.

Which of the following statements is false? 

The incorrect statement among the following regarding helium is -

1. It is used to produce and sustain powerful superconducting magnets.

2. It is used as a cryogenic agent for carrying out experiments at low temperatures.

3. It is used in filling balloons for meteorological observations because it is lighter and non-inflammable.

4. It is used as a dilute for oxygen in modern diving apparatus because of its high solubility in blood.

Assertion : $Pb{I}_4$  is not known probably because of the oxidising power of Pb(IV) and reducing power of $I^{-}$.

Reason :  Iodide stabilizes higher oxidation state.

Assertion : $P_4{O}_{10}$ is not used to dry $N{H}_3$.

Reason : $P_4{O}_{10}$ is acidic and $N{H}_3$ is basic.

Assertion : $HN{O}_3$  is stronger acid than $HN{O}_2$.

Reason : In $HN{O}_3$ there are two nitrogen to oxygen bonds where as in $HN{O}_2$ there is only one.

Assertion : $HN{O}_3$ oxides sulphur to $H_{2}S{O}_4$  acid ( S + VI) but only oxidizes selenium to $H_{2}Se{O}_3$ ( Se + IV ).

Reason : In Selenium atoms, the electrons are more tightly held by the nucleus on account of increased nuclear charge.

Assertion : Sulphur dioxide is more powerful reducing agent in alkaline medium than in acidic
medium.

Reason :  Sulphur dioxide reacts with hydrogen sulphide in presence of moisture and sulphur is
precipitated.