Redox reaction among the following is -

1. NaCl + KNO₃ $\to$NaNO₃ + KCl

2. CaC₂O₄ + 2HCl $\to$CaCl₂ + H₂C₂O₄

3. Mg(OH)₂ + 2NH₄Cl $\to$MgCl₂ + 2NH₄OH

4. Zn + 2AgCN $\to$2Ag + Zn(CN)₂

Which metal exhibits more than one oxidation states?

1. Na

2. Mg

3. Al

4. Fe

In the aluminothermic process, aluminium acts as:

1. an oxidising agent

2. a flux

3. a reducing agent

4. a solder

Disproportionation reaction(s) among the following is/are represented by -

1. Cl₂ + 2OH^- $\to$ClO^- + Cl^- + H₂O

2. Cu₂O(s) + 2H⁺ $\to$Cu²⁺ + Cu(s) + H₂O

3. 2HCuCl₂ $\underset{\mathrm{water}}{\overset{\mathrm{Dilution}<mspace\; width="1em"></mspace>\mathrm{with}}{\to }}$ Cu + Cu²⁺ + 4 Cl^- +  2H⁺

4. All of the above

In a redox change, the oxidant K₂Cr₂O₇ is always reduced to:

1. Cr⁵⁺

2. Cr⁴⁺

3. Cr³⁺

4. Cr²⁺