The oxidation state of Ni in Ni(CO)₄ is:

1. zero

2. +4

3. +8 

4. +2

Sulphurous acid can be used as:

1. Oxidising agent

2. Reducing agent

3. Bleaching agent

4. All of the above

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

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

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

1. Reducing agent

2. Oxidising agent

3. Catalytic agent

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. 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