Title 8. Redox Reactions.pdf ✅

FACT/DEFINITION TYPE QUESTIONS 1. Which of the following process takes place in oxidation process? (a) Addition of oxygen (b) Addition of hydrogen (c) Removal of oxygen (d) Addition of chlorine 2. Given reaction, 2K4 [Fe(CN)6 ] (aq) + H2O2 (aq) o 2K3 [Fe(CN)6 ](aq) + 2KOH(aq) The above given reaction is oxidation reaction due to (a) removal of a hydrogen from H2O2 (b) addition of electropositive potassium to H2O2 (c) removal of electropositive element potassium from potassium ferrocyanide (K4 [Fe(CN)6 ]) (d) All of the above are the correct reasons. 3. In the reaction given below, identify the species undergoing redox reaction 2Na(s) + H2 (g) o 2NaH(s) (a) Na is reduced and hydrogen is oxidised (b) Na is oxidised and hydrogen is reduced (c) Na undergoes oxidation and hydrogen undergoes reduction (d) Both (b) and (c) 4. The loss of electron is termed as (a) oxidation (b) reduction (c) combustion (d) neutralization 5. Which of the following is correct code for x and y in the following reaction. + 2– Na S2 o (s) x y 2Na(s) + S(s) (i) x = oxidation reaction, y = reduction reaction (ii) x = gain of two electrons, y = loss of two electrons, (iii) x = reduction reaction, y = oxidation reaction (iv) x = loss of two electrons, y = gain of two electrons (a) (i) and (ii) (b) (i) and (iv) (c) (ii) and (iii) (d) (iii) and (iv) REDOX REACTIONS 8 6. Which of the following involves transfer of five electrons ? (a) MnO o Mn (b) CrO o Cr (c) 2 MnO MnO 4 2 o (d) CrO oCr 7. Which reaction involves neither oxidation nor reduction? (a) 2 2 CrO Cr O 4 27 - - ææÆ (b) Cr CrCl ææÆ 3 (c) Na Na ææÆ + (d) 2 2 2S O S O 23 46 - - ææÆ 8. In the following reaction 4P 3KOH 3H2O o3KH 2PO 2 PH3 (a) phosphorus is both oxidised and reduced. (b) only phosphorus is reduced. (c) phosphorus is not oxidised (d) None of these 9. Which one of the following reaction involves oxidation- reduction ? (a) H Br 2HBr 2 2 o (b) NaBr HCl o NaCl HBr (c) HBr AgNO 3 o AgBr HNO 3 (d) 2NaOH H2SO4 o Na 2SO4 2H2O 10. In reaction, 4Na + O2 o 2Na2O, sodium behaves as (a) oxidising agent (b) reducing agent (c) Both (a) and (b) (d) None of these 11. 2 Zn (aq.) 2e Zn(s) o . This is (a) oxidation (b) reduction (c) redox reaction (d) None of the above 12. 2 2 Co(s) Cu (aq) Co (aq) Cu(s) o The above reaction is (a) oxidation reaction (b) reduction reaction (c) redox reaction (d) None of these 13. One mole of N2H4 loses 10 moles of electrons to form a new compound, y. Assuming that all nitrogen appear in the new compound, what is the oxidation state of nitrogen in y (There is no change in the oxidation state of hydrogen ) (a) –1 (b) –3 (c) +3 (d) +5
136 REDOX REACTIONS 14. When a strip of metallic zinc is placed in an aqueous solution of copper nitrate the blue colour of the solution disappear due to formation of (a) Cu2+ (b) Zn2+ (c) ZnS (d) Cus 15. The correct order of electron releasing tendency of the metals Cu, Zn and Ag is in the order: (a) Cu > Zn > Ag (b) Zn > Ag > Cu (c) Ag > Zn > Cu (d) Zn > Cu > Ag 16. What is the oxidation number of elements in the free or in the uncombined state ? (a) +1 (b) 0 (c) +2 (d) –1 17. In which of the following compounds oxygen has highest oxidation state and in which it has lowest oxidation state? OF2 , H2O2 , KO2 , O2 F2 (a) Highest = KO2 , lowest = H2O2 (b) Highest = OF2 , lowest = K2O2 (c) Highest = OF2 , lowest = KO2 (d) Highest = KO2 , lowest = H2O2 18. ‘Oxidation number of H in NaH, CaH2 and LiH, respectively is (a) +1, +1, –1 (b) –1, +1, + 1 (c) +1, + 1, + 1 (d) –1,–1, –1 19. Which of the following is the correct representative of stock notation for auric chloride? (a) Au(III)Cl3 (b) Au(II)Cl2 (c) Au(I)Cl2 (d) None of these 20. Oxidation number of N in HNO3 is (a) – 3.5 (b) + 3.5 (c) –5 (d) + 5 21. In which of the following reactions, there is no change in valency ? (a) 4 KClO3 o 3KClO4 + KCl (b) SO2 + 2H2 S o 2H2O + 3S (c) BaO2 + H2 SO4 o BaSO4 + H2O2 (d) 3 BaO + O2 o 2 BaO2 . 22. The oxidation number of chromium in potassium dichromate is (a) + 6 (b) – 5 (c) – 2 (d) + 2 23. The oxidation number of sulphur in S8 , S2 F2 , H2 S respectively, are (a) 0, +1 and –2 (b) +2, +1 and –2 (c) 0, +1 and +2 (d) –2, +1 and –2 24. Oxidation number of cobalt in K[Co(CO)4 ] is (a) +1 (b) +3 (c) –1 (d) –3 25. Oxidation number of nitrogen in (NH4 ) 2 SO4 is (a) –1/3 (b) –1 (c) +1 (d) –3 26. Oxidation number of carbon in CH2Cl2 is (a) –4 (b) +4 (c) 0 (d) –2 27. In which of the following compounds, iron has lowest oxidation state? (a) Fe[K CN( ]) 3 6 (b) Fe[K CN( ]) 4 6 (c) FeSO .(NH SO) OH6. 24244 (d) 5 Fe CO( ) 28. The oxidation state of osmium (Os) in OsO4 is (a) +7 (b) +6 (c) +4 (d) +8 29. Which of the following transition metal has zero oxidation state ? (a) [Fe(CO)5 ] (b) NH2 .NH2 (c) NOClO4 (d) CrO5 30. In which of the compounds does 'manganese' exhibit highest oxidation number ? (a) MnO2 (b) Mn3O4 (c) K2MnO4 (d) MnSO4 31. Among the following, identify the species with an atom in +6 oxidation state (a) – MnO (b) – CN(Cr ) (c) – NiF (d) C Cl rO 32. In which of the following compounds the oxidation number of carbon is not zero? (a) HCHO (b) CH3COOH (c) C12H22O11 (d) CH3CHO 33. In which of the following compounds, the oxidation number of iodine is fractional ? (a) IF7 (b) I (c) IF5 (d) IF3 34. A metal ion M3+ loses 3 electrons, its oxidation number will be (a) +3 (b) +6 (c) 0 (d) –3 35. The correct name for NO2 using stock notation is (a) nitrogen dioxide (b) nitrogen (iv) oxide (c) nitrogen per oxide (d) All of these 36. The oxide, which cannot act as a reducing agent, is (a) NO2 (b) SO2 (c) CO2 (d) ClO2 37. The oxidation state of Fe in Fe3O4 is (a) + 3 (b) 8/3 (c) + 6 (d) + 2 38. In oxygen difluoride, the oxidation number of oxygen is (a) – 2 (b) – 1 (c) + 2 (d) +1, – 2 39. Oxygen has an oxidation state of +2 in the compound (a) H O2 2 (b) CO2 (c) H O2 (d) F O2 EduHulk REDOX REACTIONS
REDOX REACTIONS 137 40. The number of electrons involved in the reduction of one nitrate ion to hydrazine is (a) 8 (b) 5 (c) 3 (d) 7 41. The average oxidation state of sulphur in Na2S4O6 is (a) +2.5 (b) +2 (c) +3.0 (d) +3.5 42. Which of the following species can function both as oxidizing as well as reducing agent ? (a) Cl– (b) ClO4 – (c) ClO– (d) MnO4 – 43. The oxidation number of an element in a compound is evaluated on the basis of certian rules. Which of the following rules is not correct in this respect? (a) The oxidation number of hydrogen is always + 1. (b) The algebraic sum of all the oxidation numbers in a compound is zero. (c) An element in the free or the uncombined state bears oxidation number zero. (d) In all its compounds, the oxidation number of fluorine is – 1. 44. Nitric oxide acts as a reducing agent in the reaction (a) 4NH3 5O2 o 4NO 6H2O (b) NO I HO oNO l H – – (c) 2 NO H2SO3 o N2O H2SO4 (d) NO HS o NO S HO 45. In the compounds KMnO4 and K2Cr2O7 the highest oxidation state is of the element (a) potassium (b) manganese (c) chromium (d) oxygen 46. Atomic number of an element is 22. The highest O.S. exhibited by it in its compounds is (a) 1 (b) 2 (c) 3 (d) 4 47. Why the displacement reactions of chlorine, bromine and iodine using fluorine are not generally carried out in aqueous solution? (a) chlorine, bromine and iodine reacts with water and displace oxygen of water (b) Fluorine being very reactive attacks water and displaces oxygen of water (c) Fluorine does not react with chlorine, bromine and iodine in aqueous media (d) None of these 48. Which of the following statement is not true ? (a) Displacement reaction of chlorine with Br– and I– form the basis of identifying Br– and I– in laboratory using layer test (b) F2 , Cl2 , Br2 and I2 can be recovered by halogen displacement reactions by using their respective halides (c) F2 can be recovered from F– by oxidising it electrolytically. (d) None of these. 49. Which of the following do not show disproportionation reaction? – ClO4 , F2 , Cl2 , – ClO2 , P4 , S8 , and ClO– (a) – ClO2 , – ClO4 , and ClO– (b) F2 only (c) F2 and – ClO4 (d) – ClO4 only 50. Which one of the following reactions involves disproportionation? (a) 2H2 SO4 + Cu o CuSO4 + 2H2O + SO2 (b) As2O3 + 3H2 S o As2 S3 + 3H2O (c) 2KOH + Cl2o KCl + KOCl + H2O (d) Ca3 P2 + 6H2O o 3Ca(OH)2 + 2PH3 51. The following species will not exhibit disproportionation reaction (a) ClO– (b) ClO2 (c) ClO3 (d) ClO4 52. In the reaction o 3 – 2 3 2 3Br2 6CO3 3H O 5Br BrO 6HCO (a) Bromine is oxidised and carbonate is reduced. (b) Bromine is reduced and water is oxidised (c) Bromine is neither reduced nor oxidised (d) Bromine is both reduced and oxidised 53. Which of the following elements does not show disproportionation tendency? (a) Cl (b) Br (c) F (d) I 54. Phosphorus, sulphur and chlorine undergo disproportion in the ...A... medium. Here, A refers to (a) acidic (b) alkaline (c) neutral (d) Both (a) and (b) 55. The reaction, 12 0 0 2 22 2H O( ) 2H ( ) O ( ) + - D l gg ææÆ + is an example of (a) addition reaction (b) decomposition reaction (c) displacement reaction (d) None of these 56. How will you balance the total ionic charge of reactant and products if reaction is carried out in acidic solution? (a) By using H+ ions (b) By using OH– ions (c) Adding H2O molecules to the reactant or product (d) Multiplying by suitable coefficients. 57. Consider the following reaction occuring in basic medium – – 2MnO (aq)+Br (aq) 4 o 2MnO2 (s) + Br – O3 (aq) How the above reaction can be balanced further? (a) By adding 2 OH– ions on right side (b) By adding one H2O molecule to left side (c) By adding 2H+ ions on right side (d) Both (a) and (b) EduHulk REDOX REACTIONS
138 REDOX REACTIONS 58. For the reaction : NH3 OCl o 42 ClHN in basic medium, the coefficients of NH3 , OCl– and N2H4 for the balanced equation are respectively (a) 2, 2, 2 (b) 2, 2, 1 (c) 2, 1, 1 (d) 4, 4, 2 59. C2H6 (g) + nO2 (g) o CO2 (g) + H2O(l) In this equation, the ratio of the coefficients of CO2 and H2O is (a) 1 : 1 (b) 2 : 3 (c) 3 : 2 (d) 1 : 3 60. 4 2 2 2 2 2MnO 5H O 6H 2 5O 8H O. Z o In this reaction Z is (a) Mn+2 (b) Mn+4 (c) MnO2 (d) Mn 61. In the redox reaction, xKMnO4 + NH3 o yKNO3 + MnO2 + KOH + H2O (a) x = 4, y = 6 (b) x = 3, y = 8 (c) x = 8, y = 6 (d) x = 8, y = 3 62. What is ‘A’ in the following reaction 2Fe3+(aq) +Sn2+(aq) o2Fe2+(aq) + A (a) Sn3+ (aq) (b) Sn4+ (aq) (c) Sn2+ (aq) (d) Sn 63. Given : X Na2HAsO3 + Y NaBrO3 + Z HCl o NaBr + H3AsO4 + NaCl The values of X, Y and Z in the above redox reaction are respectively (a) 2, 1, 2 (b) 2, 1, 3 (c) 3, 1, 6 (d) 3, 1, 4 64. The values of x and y in the following redox reaction Clx 2 + OH6 o ClO3 + Cly + OH3 2 are (a) x = 5, y = 3 (b) x = 2, y = 4 (c) x = 3, y = 5 (d) x = 4, y = 2 65. A negative E : means that redox couple is a ___A___ than the H+ /H2 couple A positive E : means that the redox couple is a ____B___ than H+ /H2 couple (a) A = stronger reducing agent B = weaker reducing agent (b) A = stronger oxidising agent B = weaker oxidising agent (c) A = weaker oxidising agent B = stronger oxidising agent (d) Both (a) and (c) 66. Given E 4 (i) Mg2+/Mg(s), E 4 = –2.36 (ii) Ag+ /Ag(s), E 4 = 0.80 (iii) Al3+/Al(s), E 4 = –1.66 (iv) Cu2+/Cu(s), E 4 = 0.52 Out of the above given elements which is the strongest oxidising agent and which is the weakest oxidising agent ? (a) (iv) is the strong whereas (ii) is the weakest oxidising agent (b) (ii) is the strongest whereas (i) is the weakest oxidising agent (c) (i) is the strongest whereas (ii) is the weakest oxidising agent (d) (ii) is the strongest whereas (iii) is the weakest oxidising agent 67. Stronger is oxidising agent, more is (a) standard reduction potential of that species (b) the tendency to get it self oxidised (c) the tendency to lose electrons by that species (d) standard oxidation potential of that species 68. Standard reduction potentials of the half reactions are given below : F2 (g) + 2e– o 2F– (aq); E° = + 2.85 V Cl2 (g) + 2e– o 2Cl– (aq); E° = + 1.36 V Br2 (l) + 2e– o 2Br– (aq); E° = + 1.06 V I 2 (s) + 2e– o 2I– (aq); E° = + 0.53 V The strongest oxidising and reducing agents respectively are : (a) F2 and I– (b) Br2 and Cl– (c) Cl2 and Br– (d) Cl2 and I2 69. Standard electrode potentials of redox couples A2+/A, B2+/B, C/C2+ and D2+/D are 0.3V, – 0.5V, – 0.75V and 0.9V respectively. Which of these is best oxidising agent and reducing agent respectively – (a) D2+/D and B2+/B (b) B2+/B and D2+/D (c) D2+/D and C2+/C (d) C2+/C and D2+/D 70. The standard reduction potentials at 298K for the following half reactions are given against each Zn2+ (aq) + 2e U Zn(s) ; –0.762 V Cr3+ (aq) + 3e U Cr (s); –0.740 V 2H+ (aq) + 2e U H2 (g) ; 0.00 V Fe3+ (aq) + e U Fe2+ (aq) ; 0.770 V Which is the strongest reducing agent? (a) Zn (s) (b) Cr (s) (c) H2(g) (d) Fe3+ (aq) 71. Electrode potential data are given below : FeeFe ; 2 aq( ) 3 )aq( o E° = +0.77 V (s) 3 (aq) o Ale3Al ; E° = – 1.66 V Br 2e 2Br ; )aq(2 aq( ) o E° = + 1.08V Based on the data, the reducing power of Fe2+, Al and Br– will increase in the order (a) Br– < Fe2+ < Al (b) Fe2+ < Al < Br– (c) Al < Br– < Fe2+ (d) Al < Fe2+ < Br– 72. The standard reduction potentials for Cu2+/Cu; Zn2+/Zn; Li+ /Li; Ag+ /Ag and H+ /H2 are + 0.34 V, – 0.762 V, – 3.05 V, + 0.80 V and 0.00 V respectively. Choose the strongest reducing agent among the following (a) Zn (b) H2 (c) Ag (d) Li EduHulk REDOX REACTIONS