During the laboratory preparation of chlorine gas by the reaction:
MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O
What is the role of MnO₂ in the reaction?

1.	Reducing agent	2.	Oxidising agent
3.	Catalyst	4.	Dehydrating agent

In the equation,

N${\mathrm{O}}_2^{-}$ +  H₂O $\to$N${\mathrm{O}}_3^{-}$ + 2H⁺ + ne^-

n represents

1. 5

2. 1

3. 2

4. 3

Reaction between acidified K₂Cr₂O₇ and iron (II) ions shown by the equation:

Cr₂${\mathrm{O}}_7^{2-}$(aq) + 6Fe²⁺(aq) +14H⁺(aq)$\to$2Cr³⁺(aq) + 7H₂O(l) + 6Fe³⁺(aq)

The correct statement among the following is:

1. Color of the solution changes from green to blue

2. Iron (II) ions are reduced 

3. Dichromate ions are reduced 

4. Hydrogen ions are reduced

Which metal exhibits more than one oxidation states?

1. Na

2. Mg

3. Al

4. Fe

Among the following, In which iron has the lowest oxidation state?

1. Fe(CO)₅

2. Fe₂O

3. K₄Fe(CN)₆

4. FeSO₄.(NH₄)₂SO₄.6H₂O

When an acidified solution of ferrous ammonium sulphate is treated with KMnO₄ solution, the ion that gets oxidised is:

1. Fe²⁺

2. S${\mathrm{O}}_4^{2-}$

3. N${\mathrm{H}}_4^{+}$

4. Mn${\mathrm{O}}_4^{-}$

2Na₂S₂O₃ + I₂ $\to$ Na₂S₄O₆ + 2NaI,

the oxidation state of sulphur in tha above reaction:

1. Decreases

2. Increases

3. Remain unchanged

4. None of the above

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

1. Cr⁵⁺

2. Cr⁴⁺

3. Cr³⁺

4. Cr²⁺

Which of the following reactions does not represent a redox change?

1. CaCO₃ $\to$CaO + CO₂

2. 2H₂ + O₂ $\to$2H₂O

3. Na + H₂O $\to$ NaOH + \(\frac{1}{2}\)H₂

4. MnCl₃ $\to$ MnCl₂ + \(\frac{1}{2}\)Cl₂

In the reaction;

3Br₂ + 6C${\mathrm{O}}_3^{2-}$ + 3H₂O $\to$5Br^- + Br${\mathrm{O}}_3^{-}$ + 6HC${\mathrm{O}}_3^{-}$

Which of the following statements is correct?

1. Br₂ is only oxidised.

2. Br₂ is only reduced

3. Br₂ is neither oxidised nor reduced

4. Br₂ is both oxidised and reduced.