The role of an electrolyte in the  preparation of H₂ by electrolytic method is:

The products obtained on the completion of the following reactions (i) and (ii) respectively are :

1. A = CO, and H₂ ; B = Na₂ZnO₂
2. A  = CO₂ ; B = Na₄ZnO₄
3. A = CH₃CH₂CH₂OH ; B=  ZnO
4. None of the above

The correct statement among the following regarding hydrogen is–

1. It can form a bond in +1 as well as –1 oxidation state

2. It is always collected at the cathode

3. It has a very low ionization potential

4. It has the same electronegativity as halogens

When substance A reacts with water, it produces a combustible gas B and a solution of substances 'C' in water. When another substance 'D' reacts with this solution of C, it produces the same gas 'B' on warming but 'D' can produce gas 'B' on reaction with dilute sulphuric acid at room temperature. 'A' imparts a deep golden yellow colour to a smokeless flame of a bunsen burner. A, B, C and D respectively are -

1. $\mathrm{Na},$ ${\mathrm{H}}_2,$ $\mathrm{NaOH},$ $\mathrm{Zn}$                              

2. $\mathrm{K},$ ${\mathrm{H}}_2,$ $\mathrm{KOH},$ $\mathrm{Al}$

3. $\mathrm{Ca},$ ${\mathrm{H}}_2,$ $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2,$ $\mathrm{Sn}$                           

4. ${\mathrm{CaC}}_2,$ ${\mathrm{C}}_2{\mathrm{H}}_2,$ $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2,$ $\mathrm{Fe}$

Dihydrogen gas cannot be prepared with-

1. Cu + HCl (dil.)

2. Fe + H₂SO₄

3. Mg + steam

4. Na + alcohol