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

1. Os

2. Ru

3. Xe

4. All of the above

Equation that does not represent a redox reaction is-

1. BaO₂ + H₂SO₄ $\to$BaSO₄ +  H₂O₂ 

2. 2BaO + O₂ $\to$ 2BaO₂ 

3. 2KClO₃ $\to 2$KCl + 3O₂ 

4. SO₂ + 2H₂S $\to$2H₂O + 3S

In the preparation of chlorine from HCl;  MnO₂ acts as:

1. Reducing agent

2. Oxidising agent

3. Catalytic agent

4. Dehydrating agent

Excess of KI reacts with CuSO₄ solution and then Na₂S₂O₃ solution is added to it. Which of the statement is incorrect in this reaction?

1. Evolved I₂ is reduced

2. CuI₂ is formed

3. Na₂S₂O₃ is oxidised

4. Cu₂I₂ is formed

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

Amount of oxalic acid present in a solution can be determined by its titration with KMnO₄ solution in the presence of H₂SO₄. The titration gives unsatisfactory result when carried out in the presence of HCl, because HCl:

1. oxidises oxalic acid to carbon dioxide and water

2. gets oxidised by oxalic acid to chlorine

3. furnishes H⁺ ions in addition to those from oxalic acid

4. reduces permanganate to Mn²⁺

KMnO₄ in acidic medium is always reduced to:

1. Mn⁴⁺ 

2. Mn²⁺ 

3. Mn⁶⁺

4. Mn

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

The oxidation number of carbon in C₃O₂  and Mg₂C₃ are respectively:

1. -4/3, +4/3 

2. +4/3, -4/3

3. -2/3, +2/3

4. -2/3, +4/3

Which metal exhibits more than one oxidation states?

1. Na

2. Mg

3. Al

4. Fe