In which reaction hydrogen is not formed ?

(1) Copper and hydrochloric acid

(2) Iron and sulphuric acid

(3) Magnesium and steam

(4) Sodium and alcohol

Which conversion is not done by H₂O₂ ?

(1) ${\mathrm{Fe}}^{2+} \stackrel{ }{\to }{\mathrm{Fe}}^{3+}$(acidic medium)

(2) $\mathrm{PbS}\stackrel{ }{\to }{\mathrm{PbSO}}_4$

(3) ${\mathrm{Fe}}^{1+} \stackrel{ }{\to }{\mathrm{Fe}}^{3+}$ (alkaline medium)

(4) $\mathrm{KI} \stackrel{ }{\to }{\mathrm{I}}_2$

H₂O₂ restores the colour of old lead paintings, blackened by the action of H₂S gas, by:

(1) converting PbO₂ to Pb

(2) oxidising PbS to PbSO₄

(3) converting PbCO₃ to Pb

(4) oxidizing PbSO₃ to PbSO₄

(I) ${\mathrm{H}}_2{\mathrm{O}}_2+{\mathrm{O}}_3 \stackrel{ }{\to }{\mathrm{H}}_2\mathrm{O} + 2{\mathrm{O}}_2$

(II) ${\mathrm{H}}_2{\mathrm{O}}_2 + {\mathrm{Ag}}_2\mathrm{O} \stackrel{ }{\to }2\mathrm{Ag} + {\mathrm{H}}_2\mathrm{O} + {\mathrm{O}}_2$

Role of hydrogen peroxide in the above reactions is respectively

(a) oxidising in (I) and reducing in (II)

(b) reducing in (I) and oxidising in (II)

(c) reducing in(I) and  (II)

(d) oxidising in(I) and (II)

In acidic medium, H₂O₂ changes ${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$ to CrO₅ which has two (-O-O-) bonds. Oxidation state of Cr in CrO₅ is

(a) +5

(b) +3

(c) +6

(d) -10

Nascent hydrogen consists of $-$

(A) Hydrogen atoms with excess energy

(B) Hydrogen molecules with excess energy

(C) Hydrogen ions in the excited state

(D) Solvated protons

Maximum concentration of ortho-$H_2$ in ordinary hydrogen is:

(1) 75% ortho-$H_2$ + 25% para-$H_2$

(2) 25% ortho-$H_2$ + 75% para-$H_2$

(3) 50% ortho-$H_2$ + 50% para-$H_2$

(4) 99% para-$H_2$ + 1% ortho-$H_2$

Blackened oil planting can be restored into original form by the action of:

1. Chlorine

2. ${\mathrm{BaO}}_2$

3. ${\mathrm{H}}_2{\mathrm{O}}_2$

4. ${\mathrm{MnO}}_2$

Which of the following statement regarding ${\mathrm{H}}_2{\mathrm{O}}_2$ is wrong.

(1) It is stable in acid medium

(2) It acts as oxidising as well as reducing agent

(3) It has zero dipole moment

(4) Pure ${\mathrm{H}}_2{\mathrm{O}}_2$ is slightly acidic

${\mathrm{H}}_2\mathrm{O}$ has higher boiling point than ${\mathrm{H}}_2\mathrm{S}$ because.

(1) ${\mathrm{H}}_2\mathrm{O}$ is a smaller molecule and hence more closely packed

(2) The bond angle in ${\mathrm{H}}_2\mathrm{O}$ is more than in ${\mathrm{H}}_2\mathrm{S}$ and hence the former molecules are more tightly packed

(3) Of intermolecular hydrogen bonding in liquid ${\mathrm{H}}_2\mathrm{O}$

(4) The latent heat of vaporisation is higher for ${\mathrm{H}}_2\mathrm{O}$ than for ${\mathrm{H}}_2\mathrm{S}$