1. How many electrons are needed to balance the equation?
(b) 6 electrons are needed to balance the charge in the redox reaction. 2. In the following equation, the value of X is[MOE 2002]
(a) 2 electrons (2e) are required to balance the equation. 3. When SO2 is passed through acidified KMnO4 solution, solution is turned green because[IOM 2005]
- KMnO4 is oxidized
- KMnO4 solution is turned green
- SO2 is reduced
- KMnO4 is reduced
(d) KMnO4 (purple) is reduced to Mn2+ (green) by SO2. 4. In the reaction, which is the element that is reduced?[MOE 2064]
(c) Mn (in MnO4-) is reduced from +7 to +2 oxidation state. 5. A solution of SO2 in water reacts with H2S precipitating sulfur. Here SO2 acts as[MOE 2058]
- A catalyst
- An acid
- An oxidizing agent
- A reducing agent
(c) SO2 oxidizes H2S to sulfur (S), acting as an oxidizing agent. 6. In the reaction, which one is reduced?[MOE 2008]
(a) Cr (in Cr2O72-) is reduced from +6 to +3 oxidation state. 7. Which one is oxidized in the following reaction?[MOE 1997]
- Cu is oxidized
- Cu is reduced
- S is oxidized
- S is reduced
(a) Cu (0) is oxidized to Cu2+ in the reaction. 8. Oxidation state of oxygen atom in potassium superoxide is[BPKIHS 1994]
(b) In KO2 (potassium superoxide), oxygen has -1/2 oxidation state. 9. In the Alumino-thermic process of manufacture of Aluminium, aluminium acts as[BPKIHS 2006]
- Reducing agent
- Oxidizing agent
- Both
- Complexing agent
(a) Aluminium acts as a reducing agent to reduce metal oxides. 10. Oxygen has a positive oxidation state in[BPKIHS 2005]
(c) In F2O, oxygen has +2 oxidation state (fluorine is more electronegative). 11. The reaction is[BPKIHS 2000]
- Oxidation reaction
- Reduction reaction
- Neutralization reaction
- Disproportionation reaction
(d) The reaction involves both oxidation and reduction of the same element (disproportionation). 