REDOX REACTIONS AND ELECTROCHEMISTRY – 5

1) The oxidation number of S in S2Cl2 is
a) +1
b) +6
c) 0
d) -1

2) Which one of the following cannot be oxidised ?
a)
b) NO
c)
d)

3) A reducing agent is one which
a) Donates protons
b) Donates electrons
c) Accepts electrons
d) Neither accepts nor donates electrons

4) In the reaction 2Na2S2O3 + I2Na2S4O6+2NaI, the oxidation state of sulphur is
a) Decreased
b) Increased
c) Unchanged
d) None

5) The reaction H2S + H2O2 2H2O + S shows the
a)
b)
c)
d)

6) In C + H2O CO + H2 , H2O acts as a/an
a) Oxidising agent
b) Reducing agent
c) Both
d) None

7) Indicate in which of the following processes the nitrogen is oxidised,
a)
b)
c)
d)

8) The maximum oxidation number of a transition metal is
a) +4
b) +6
c) +8
d) +10

9) The oxidation state of Fe in Fe3O4 is
a) +3
b) +6
c) +2 and +3
d) +2

10) The oxidation state of Mn in Ca(MnO4)2 is
a) -2
b) +2
c) +4
d) +7

11) Which of the following is a mild oxidising agent ?
a)
b)
c)
d)

12) The oxidation number of sodium in sodium amalgam is
a) +2
b) +1
c) -2
d) 0

13) The most common oxidation state of an element is -2. The number of electrons present in its outermost shell is

a) 2
b) 4
c) 6
d) 8

14) Which one of the following is an oxidising agent in the reaction ?
a)
b)
c)
d) None

15) Which reaction involves neither oxidation nor reduction ?
a) Burning tin in chlorine gas
b) Reaction of Fe with S
c)
d)

16) In the reaction of O3 and H2O2, the latter acts as a/an
a) Oxidising agent
b) Reducing agent
c) Bleaching agent
d) Both oxidising and bleaching agent

17) Sulphurous acid can be used as a/an
a) Oxidising agent
b) Reducing agent
c) Bleaching agent
d) All the above

18) The oxidation number of P in KH2PO2 is
a) +l
b) +3
c) -3
d) +5

19) The oxidation number of Mn in MnO42- is
a) – 2
b) + 2
c) + 6
d) + 8

20) One mole of N2H4 loses 10 mole of electrons to form a new compound Y. Assuming that all nitrogen appears in the new compound, what is the oxidation number of nitrogen in Y (There is no change in the oxidation state of hydrogen)?
a) -3
b) +3
c) +5
d) +1

21) The oxidation state of nitrogen in NH4NO3 is
a) -3 and +5
b) +3 and +5
c) +5
d) +3

22) In the reduction of dichromate by iron II, the number of electrons involved per chromium atom is
a) One
b) Three
c) Four
d) Two

23) In the reaction Cl2 + OHCl+ ClO3 + H2O
a) Chlorine is oxidised
b) Chlorine is reduced
c) Chlorine is oxidised as well as reduced
d) Chlorine is neither oxidised nor reduced

24) Nitrogen can have oxidation number -3 to +5. Identify the compound having nitrogen in +1 state.
a)
b) NO
c)
d)

25) The oxidation number of chlorine in HOCl is
a) 0
b) – 1
c) +1
d) +2

26) The oxidation state of +3 for phosphorus is in
a) Hypophosphorus acid
b) Meta phosphoric acid
c) Ortho phosphoric acid
d) Phosphorus acid

27) An oxyacid of phosphorus which is dibasic as well as a reducing agent is
a)
b)
c)
d)

28) Which of the following is a redox reaction ?
a)
b)
c)
d)

29) The element with the atomic number 9, which can exhibit an oxidation number is
a) +1
b) -1
c) -1 and -2
d) -1 and +1

30) When an acidified solution of ferrous ammonium sulphate is treated with KMnO4 solution, the ion which is oxidised is
a)
b)
c)
d)

31) The oxidation number of N in N2H5+ is
a) -2
b) +3
c) +2
d) -3

32) The charge on cobalt in [Co(CN)6]3- is
a) – 6
b) +3
c) -3
d) +6

33) In the reaction Cu(s) + 2Ag+(aq) Cu2+(aq)+2Ag(s)
a)
b)
c)
d)

34) The oxidation number of carbon in H2C2O4 is
a) +2
b) +3
c) +4
d) +1

35) In the equation MnO4 + 5Fe2++ 8H+ Mn2++5Fe3+ +4H2O, the oxidation number of Mn
a) Increases from – 1 to – 2
b) Decreases from +3 to +2
c) Decreases from +7 to +2
d) Remains unchanged

36) Which of the following serves as a reducing agent in the reaction ?

14H++ Cr2O72-+ 3Ni 2Cr3++ 7H2O+ 3Ni2+
a)
b) Ni
c)
d)

37) The most powerful oxidising agent among the following is

a)
b)
c)
d)

38) Iodine oxidises the S2O32- ion to
a)
b)
c)
d)

39) Which of the following reactions does not involve either oxidation or reduction ?
a)
b)
c) 2Cr2O72- Cr2O72-
d)

40) Which of the following acids is strongest ?
a)
b) HOCl
c)
d)

41) The element which can never act as a reducing agent in a chemical reaction is
a) O
b) Li
c) F
d) C

42) In the reaction 3Cl2 + 6NaOH 5NaCl + NaClO3 + H2O Â
a)
b)
c)
d)

43) In which of the following does H2O2 act as a reducing agent ?
a)
b)
c)
d)

44) On passing H2S gas in II group sometimes the solution turns milky. It indicates the presence of a/an
a) Oxidising agent
b) Acidic salt
c) Reducing agent
d) Thiosulphate

45) The most common oxidation number of an element is -1. The number of electrons in its outermost orbit is
a) 7
b) 8
c) 1
d) 4

46) One gas bleaches the colour of the flowers by reduction while the other does so by oxidation. The gases are
a)
b)
c)
d)

47) Which is the reducing agent in the reaction, 8H++ 4NO3 + 6Cl + Sn(s) SnCl62-+ 4NO2+ 4H2O ?
a) Sn (s)
b)
c)
d)

48) In the reaction 2KMnO4+ 16HCl 2KCl + 2MnCl2 + 8H2O + 5Cl2, the reduction product is
a)
b)
c) KCl
d)

49) H2S reacts with halogens. The halogens are
a) Oxidised
b) Reduced
c) Form sulphur halides
d) None of these take place

50) A sulphur containing species that cannot be an oxidising agent is
a)
b)
c)
d)

51) Ozone tails mercury. The reaction is
a) Reduction
b) Oxidation
c) Substitution
d) None

52) A sulphur containing species that cannot be a reducing agent is
a)
b)
c)
d)

53) Chromium has the most stable oxidation state in
a) +5
b) +3
c) +2
d) +4

54) Th oxidation number of Mn in K2MnO4 and MnSO4 is respectively.
a) +7 and +2
b) +6 and +2
c) +5 and +2
d) +2 and +6

55) Stannous chloride gives a white precipitate with a solution of mercuric chloride. In this process mercuric chloride is
a) Oxidised
b) Reduced
c) Converted into a complex compound containing Sn and Hg
d) Converted into a chloro complex of Hg

56) In the rusting of iron, 4Fe + 3O2 2Fe2O3, iron is
a) Oxidised
b) Reduced
c) Hydrolysed
d) Precipitated

57) With respect to O2, I2 exhibits a maximum valency of
a) +5
b) +7
c) +1
d) -1

58) Carbon reacts with oxygen to form two oxides, CO and CO2. This is because
a) Carbon has two crystalline forms
b) Carbon has two oxidation states
c) Carbon donates as well as accepts electrons
d) Oxygen has a strong affinity for carbon

59) Which is a strong reducing agent ?
a) Hydrogen iodide
b) Sodium hypochlorite
c) Ferric chloride
d) Potassium bromide

60) The oxyacid which acts both as oxidising and reducing agent is
a)
b)
c)
d)

61) As the oxidation state for any metal increases, the tendency to show ionic character
a) Decreases
b) Increases
c) Remains same
d) None

62) In the reaction H2O2 + Na2CO3 Na2O2 + CO2 + H2O, the substance undergoing oxidation is
a)
b)
c)
d) None

63) Which is not a redox change ?
a)
b)
c)
d)

64) The oxidation states of the most electronegative element in the products of the reaction between BaO2 + H2SO4 are.
a) 0 and – 1
b) – 1 and – 2
c) – 2 and 0
d) – 2 and + 1

65) The reaction KI +I2 KI3 shows.
a) Oxidation
b) Reduction
c) Complex formation
d) All the above

66) The oxidation number of Fe in ferrous ammonium sulphate
a) + 3
b) + 2
c) 0
d) – 2

67) How many moles of electrons are involved in the reduction of one mole of MnO4 ion in an alkaline medium to MnO3 ?
a) 2
b) 1
c) 5
d) 3

68) The oxidation number of iodine in IF5 is
a) + 5
b) – 5
c) – 1
d) + 1

69) In the reaction CH3OH HCOOH, the number of electrons that must be added to the right are
a) 4
b) 3
c) 2
d) 1

70) In balancing the half reaction S22+S(s), the number of electrons that must be added is
a) 2 on the right
b) 2 on the left
c) 3 on the right
d) 4 on the left

71) The oxidation number of S in Na2S4O6 is
a) +6 and -1 (Two S in +6 state, Two S in -1 state)
b) + 2 and + 3 (two S have + 2 and the other 2 have + 3)
c) + 2 and + 3 (three S have + 2 and one S has + 3)
d) + 5 and 0 (two S have + 5 and the other two have S = 0)

72) The oxidation state of Fe in sodium nitroprusside Na2[Fe(CN)5 NO] is

a) + 2
b) + 1
c) 0
d) + 3

73) The oxidation number of As in arsenates is
a) +5
b) + 4
c) + 6
d) +3

74) The oxidation number of Ba in BaO2 is
a) +2
b) – 1
c) + 4
d) + 6

75) In which of the following compounds is the oxidation number of iodine 0 and -1 ?
a)
b)
c)
d)

76) The oxidation number of S8, S2F2 and H2S are respectively
a) 0, + 1 and – 2
b) + 2, + 1 and – 2
c) 0, + 1 and + 2
d) – 2, + 1 and – 2

77) The oxidation numbers of Fe in Fe3O4 are
a) + 2 and + 3
b) + 1 and + 2
c) + 1 and + 3
d) + 2 and + 2

78) The oxidation number of phosphorus in Ba(H2PO4)2 is
a) + 3
b) + 2
c) + 5
d) +1

79) The number of electrons lost or gained during the change Fe + H2O Fe3O4 + H2 is
a) 2
b) 6
c) 4
d) 8

80) The oxidation number of S in (CH3)2SO is
a) 0
b) + 1
c) + 2
d) + 3

81) The co-ordination number and oxidation state of Cr in K3Cr(C2O4)3 is
a) 3 and + 3
b) 3 and 0
c) 6 and + 3
d) 4 and + 2

82) The oOxidation number of S in H2SO5 is
a) + 8
b) + 2
c) + 6
d) + 4

83) The oxidation number of Fe in Na2 [Fe(CN)5NO] is
a) + 2
b) + 1
c) + 3
d) – 2

84) The oxidation number of Cl in NOClO4 is
a) + 7
b) – 7
c) + 5
d) – 5

85) The oxidation number of Cr in CrO5 is
a) + 6
b) + 10
c) + 4
d) + 5

86) The equivalent weight of NH3 in the reaction N2 NH3 is
a) 17/6
b) 17
c) 17/3
d) 17/2

87) The equivalent weight of N2 in the reaction N2 NH3 is.
a) 28/6
b) 28
c) 28/2
d) 28/3.

88) The oxidation number of carbon – carbon sub-oxide (C3O2) is
a) + 2/3
b) + 4/3
c) + 4
d) – 4/3

89) The equivalent weight of FeC2O4 in the change

FeC2O4Fe3 + + CO2 is
a) M/3
b) M/6
c) M/2
d) M

90) The oxidation number of Cl in CaOCl2 is
a) – 1 and + 1
b) + 2
c) – 2
d) 0

91) The oxidation number of N in NOCl is
a) + 3
b) + 2
c) + 1
d) + 4

92) The oxidation number of Fe in Fe0.94O is
a) 200
b) 200/94
c) 94/200
d) None

93) The oxidation number of cobalt in K [Co(CO)4] is
a) + 1
b) + 3
c) – 1
d) – 3

94) The number of moles of K2Cr2O7 reduced by one mole of Sn2 + ions is
a) 1/3
b) 3
c) 1.6
d) 6

95) KMnO4 acts as an oxidant in neutral, alkaline and acidic media. The final products obtained from it in the three conditions are respectively
a)
b)
c)
d)

96) 2.5 mole of hydrazine (N2H4) loses 25 mole of electrons in being converted to 5 moles of a new compound X. Assuming that all of these nitrogens appear in the new compound, what is the oxidation state of nitrogen in compound X?
a) – 1
b) – 2
c) + 3
d) + 4

97) When SO2 is passed through an acidified solution of potassium

dichromate, then chromium sulphate is formed. The change in oxidation number of Cr is
a) +4 to + 2
b) + 5 to + 3
c) + 6 to + 3
d) + 7 to + 2

98) In the reaction, which element is reduced?
a) I
b) O
c) Cr
d) H

99) The electrode potential of an electrode is
a) The potential applied to the electrode
b) The ionisation potential of the material of the electrode
c) The tendency of the electrode to lose or gain electrons when it is in contact with its ions.
d) The potential energy of the electrons in an electrode.

100) Which one of the following statements is incorrect ?
a) The tendency of an electrode to lose electrons with respect to normal hydrogen electrode is called its oxidation potential.
b) The standard oxidation potentials are taken as +ve whereas standard reduction potentials are taken as -ve
c) Oxidation potential and reduction potential of an electrode are equal in magnitude
d) The absolute value of the electrode potential cannot be determined


Answer :

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