When SO₂ is passed through acidified solution of potassium dichromate, then chromium sulphate is formed. The change in oxidation number of chromium is:

1. +4 to+2 

2. +5 to+3

3. +6 to+3

4. +7 to+2

The reaction involving the transfer of five electrons is -

1. Mn${\mathrm{O}}_4^{-}$ $\to$ Mn²⁺

2. Cr${\mathrm{O}}_4^{2-}$ $\to$Cr³⁺

3. Mn${\mathrm{O}}_4^{-}$ $\to$ MnO₂

4. Cr₂${\mathrm{O}}_7^{2-}$ $\to$2Cr³⁺

In the reaction;

2Ag + 2H₂SO₄ $\to$Ag₂SO₄ + 2H₂O + SO₂, H₂SO₄ acts as:

1. Oxidizing agent

2. Reducing agent

3. Dehydrating agent

4. None of the above

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

In which reaction H₂O₂ acts as a reducing agent?

1. Ag₂O + H₂O₂ $\to$2Ag + H₂O + O₂

2. 2KI + H₂O_2 $\to$2KOH + I₂

3. PbS + 4H₂O_2 $\to$PbSO₄ + 4H₂O₂

4. H₂O₂ + SO₂  $\to$H₂SO₄

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⁺