Redox reaction is also known as an oxidation-reduction reaction. It involves the transfer of electrons between two species. The loss of electrons is called oxidation and the gain of electrons is called reduction. There are mainly three types of redox reactions, combustion, disproportionation and single replacement. Redox reactions are widely used in the industries, e.g. pharmaceutical, metallurgical, agricultural, etc.
1. Which of the compounds can exist together?
(a) HgCl2, SnCl2
(b) FeCl3, KI
(c) FeCl3, SnCl2
(d) FeCl2, SnCl2
Answer: (d)
2. One mole of ferrous oxalate requires____ moles of MnO4– to get oxidised completely in an acidic medium
(a) 0.6 moles
(b) 0.4 moles
(c) 0.2 moles
(d) 7.5 moles
Answer: (b)
3. H2O2 changes Cr2O72- ion to CrO5 in an acidic medium, the oxidation state of Cr in CrO5 is
(a) +6
(b) +5
(c) -10
(d) +3
Answer: (a)
4. H2SO4 acts as a strong oxidising agent. In which of the reaction, is it not acting as an oxidising agent?
(a) C + 2H2SO4 → CO2 + 2SO2 + 2H2O
(b) CaF2 + 2H2SO4 → CaSO4 + 2HF
(c) S + 2H2SO4 → 3SO2 + H2O
(d) Cu + 2H2SO4 → CuSO4 + SO2 + 2H2O
Answer: (b)
5. During a reaction of oxalic acid, potassium chlorate and sulphuric acid, the oxidation number of which of the element undergoes a maximum change
(a) H
(b) S
(c) C
(d) Cl
Answer: (d)
6. Find the redox reaction
(a) In the atmosphere, O3 from O2 by lighting
(b) The reaction of H2SO4 with NaOH
(c) Both oxidation and reduction reaction
(d) Evaporation of water
Answer: (c)
7. Find the oxidation state of I in H4IO6–
(a) +7
(b) +5
(c) +1
(d) -1
Answer: (a)
8. In which of the following complex, the oxidation number of Fe is +1?
(a) Fe4[Fe(CN)6]3
(b) [Fe(H2O)5NO]SO4
(c) [FeBr4]–
(d) [Fe(H2O)6]2-
Answer: (b)
9. Which among the following compounds is the most reducing compound?
(a) H2S
(b) HNO2
(c) SnCl2
(d) H2SO3
Answer: (a)
10. Which among the following is the strongest oxidising agent?
(a) H2O2
(b) O3
(c) K2Cr2O7
(d) KMnO4
Answer: (b)
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