Which role does SO₂ play when an aqueous solution of SO₂ reacts with H₂S to precipitate sulfur?

1. Catalyst

2. Reducing agent

3. Oxidising agent

4. Acid

In the reaction;

2Ag + 2H₂SO₄ $\to$Ag₂SO₄ + 2H₂O + SO_2.
What role does H₂SO₄ play?

1. Oxidizing agent

2. Reducing agent

3. Dehydrating agent

4. None of the above

Find the values of X and Y in the balanced reaction:

X HI + Y HNO₃ $\to$NO + I₂ + H₂O

1. X=3, Y=2

2. X=2, Y=3

3. X=6, Y=2

4. X=6, Y=1

Which of the following is not an intramolecular redox reaction?

1. NH₄NO₂ $\to$N₂ + 2H₂O

2. 2Mn₂O₇ $\to$4MnO₂ + 3O₂

3. 2KClO₃ $\to$2KCl + 3O₂

4. $2{\mathrm{H}}_2{\mathrm{O}}_2$ $\to$2H₂O + O₂

Find the values of X and Y using the principle of redox balancing in an alkaline medium.

C₂H₅OH + X I₂ + Y OH^- $\to$CHI₃ + HCO₂^- + 5I^- + 5H₂O

1. 4,6

2. 2,6

3. 2,4

4. 4,4