Redox Reactions - Test Papers

CBSE TEST PAPER 01

CLASS XI CHEMISTRY
(Redox Reactions)

General Instruction:

All questions are compulsory.
Marks are given alongwith their questions.

1. Define oxidation reaction? [1]

2. Define reduction reaction? [1]

3. In the reactions given below, identify the species undergoing oxidation and reduction.

$H_{2} S (g) + C l_{2} (g)$ $\to$ $2 H C l (g) + S_{(s)}$ [1]

4. What is the most essential conditions that must be satisfied in a redox reaction? [1]

5. In the reaction

$M n O_{2} + 4 H C l \to$ $M n C l_{2} + C l_{2} + 2 H_{2} O$

Which species is oxidized? [1]

6. Why the following reaction is an example of oxidation reaction?

$C H_{4} (g) + 2 O_{2} (g) \to$ $C O_{2} (g) + 2 H_{2} O$ [1]

7. Explain why

$3 F e_{3} O_{4} (S) + 8 A l (S) \to$ $9 F e (S) + 4 A l_{2} O_{3}$

Is an oxidation reaction? [3]

CBSE TEST PAPER 01
CLASS XI CHEMISTRY (Redox Reactions)
[ANSWERS]

Ans 1. Addition of oxygen /electronegative element to a substance or removal of hydrogen / electropositive element from a substance.

Ans 2. Removal of oxygen / electronegative element form a substance or addition of hydrogen / electropositive element to a substance.

Ans 3. $H_{2} S$ is oxidized because a more electronegative element, Chlorine is added to hydrogen (or more electropositive element hydrogen has been removed from S). Chlorine is reduced due to addition of hydrogen to it.

Ans 4. In a redox reaction, the total number of electrons lost by the reducing agent must be equal to the number of electrons gained by the oxidizing agent.

Ans 5. HCl is oxidized to $C l_{2}$ .

Ans 6. Methane is oxidized owing to the addition of oxygen to it.

Ans 7. Aluminum is oxidized because oxygen is added to it Ferrous ferric oxide $(F e_{3} O_{4})$ is reduced because oxygen has been removed from it.