Which of the following shows the highest oxidation number in the combined state?

1. Os

2. Ru

3. Xe

4. All of the above

During the laboratory preparation of chlorine gas by the reaction of hydrochloric acid with manganese dioxide, the role of MnO₂ is:

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. Colour 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