CBSE Class 11 Chemistry HOTs Redox Reactions

Question. Sn⁺⁺ loses two electrons in a reaction. What will be the oxidation number of tin after the reaction?
a. + 2
b. Zero
c. + 4
d. – 2
Answer : C

Question. 2MnO^-₄ + 5H₂O₂ + 6H⁺  → 2 Z + 5O₂ + 8H₂O In this reaction Z is:
a. Mn⁺²
b. Mn⁺⁴
c. MnO₂
d. Mn
Answer : A

Question. For decolourization of 1 mole of KMnO₄₊ , the moles of H₂O₂ required is:
a. 1/2
b. 3/2
c. 5/2
d. 7/2
Answer : C

Question. Which of the following reactions represent disproportionation?
a. F₂ + NaOH → NaF + H₂O + O₂
b. 2Cu⁺ → Cu⁺² + Cu(s) 
c. 2H₂O₂ (l) → 2H₂O (l) +O₂ (g)
d. Cl2 + H₂O → HCl + HOCl
Answer : B, C, D

Question. For the balanced redox reaction aNO^-₃ bAs₂S₃ + 4H₂O → xAsO^3-₄ + yNO + zSO^2-₄ + 8H Which of the following statements are correct?
a. Equivalent weight of 2 3 As S is M/24 where ‘M’ is molecular weight of As₂ S₃
b. The value of a : b = 8 :1
c. The value of b+2b/x+y is 1
d. The value of z-x/3 is 1
Answer : C, D

Question. What is ‘A’ in the following reaction?
2Fe³⁺_(aq) + Sn²⁺_(aq) → 2Fe²⁺_(aq) + A ?
a. Sn³⁺_(aq)
b. Sn⁴⁺_(aq)
c. Sn²⁺_(aq)
d. Sn
Answer : B

Question. Which of the following reactions do not involve oxidation reduction?
a. 2Rb + 2H₂O → 2RbOH + H₂
b. 2CuI₂ → 2CuI + I₂
c. 2 NH₂Cl + NaOH → NaCl + NH₃ + H₂O
d. 4KCN + Fe(CN₂) → K₄[Fe(CN)₆]
Answer : C, D

Question. Oxidation numbers of carbon is correctly given for:
Compound       O. No.
a. HN ≡ C           + 2
b. H −C ≡ N        + 4
c. CCl₄                + 4
d. C₆H₁₂O₆            0
Answer : C, D

Question. When Cl₂ is passed through NaOH in cold, the oxidation number of Cl changes from: 
a. 0 to –1
b. 0 to +1
c. 0 to –2
d. 0 to +2
Answer : A, B

Question. H₂S acts only as a reducing agent while SO₂ can act both as a reducing and oxidizing agent because:
a. S in H₂ S has –2 oxidation state
b. S in SO₂ has oxidation state + 4
c. Hydrogen in H₂S more +ve than oxygen
d. Oxygen is more – ve in SO₂
Answer : A, B

Question. K₄[Fe(CN)6] + H₂SO₄ + H₂O →
K₂SO₄ + FeSO₄ + (NH₄) + SO₂ + CO₂
For the above reaction which statement is/are correct?
a. Oxidation number of C changes from + 2 to + 4
b. The above reaction is called acidic hydrolysis.
c. The above reaction is called disproportionation reaction.
d. n-factor for 4 6 K [Fe(CN) ] is 12.
Answer : A, C

Question. Which of the following is a redox reaction?
a. NaCl +KNO₃ → NaNO₃ + KCl
b. CaC₂O₄ + 2HCl → CaCl + H₂C₂O₄
c. Mg(OH)₂ + 2NH₄Cl → MgCl₂ + 2NH₄OH
d. Zn + 2AgCN → 2Ag + Zn(CN)₂
Answer : D

Question. In the reaction H₂S+ NO₂ → H₂O+ NO+S. H₂S is:
a. Oxidised
b. Reduced
c. Precipitated
d. None of these
Answer : A

Question. In the course of a chemical reaction an oxidant:
a. Loses electrons
b. Gains electrons
c. Both loses and gains electron
d. Electron change takes place
Answer : B

Question. In the reaction I₂ + 2S₂O⁻₃ → 2I⁻ + S₄O⁻₆  equivalent weight of iodine will be equal to:
a. 1/2 of molecular weight
b. Molecular weight
c. 1/4 of molecular weight
d. None
Answer : A

Question. The equivalent weight of KIO₃ in the reaction 2Cr(OH)₃ + 4OH + KIO₃ → 2CrO^2-₄ + 5H₂O + KI is:
a. Mole wt.
b. Mol. wt./6
c. Mol. wt./2
d. Mol. wt./3
Answer : D

Question. In alkaline medium ClO₂ oxidize H₂O₂ in O₂ and reduced itself in Cl⁻ then how many mole of H₂O₂ will oxidize by one mole of ClO₂ :
a. 1.0
b. 1.5
c. 2.5
d. 3.5
Answer : C

Question. Equation H₂S+ H₂O₂ → S+ 2HO₂ represents:
a. Acidic nature of H₂O₂
b. Basic nature of H₂O₂
c. Oxidising nature of H₂O₂
d. Reducing nature of H₂O₂
Answer : C

Question. A reducing agent is a substance which can:
a. Accept electron
b. Donate electrons
c. Accept protons
d. Donate protons
Answer : B

Question. A solution of sulphur dioxide in water reacts with H₂S precipitating sulphur. Here sulphur dioxide acts as:
a. As oxidising agent
b. A reducing agent
c. An acid
d. A catalyst
Answer : A

Question. In which of the following reactions H₂O₂ is a reducing agent?
a. 2FeCl₂ + 2HCl + H₂O₂ → 2FeCl₂ + 2H₂O
b. Cl₂ + H₂O₂ →2HCl +O
c. 2HI + H₂O₂ → 2H O+ l₂
d. H₂SO₃ + H₂O₂ → H₂SO₄ + H₂O
Answer : B

Question. Which is the best description of the behaviour of bromine in the reaction given below?
H₂O+ Br₂ → HOBr + HBr
a. Oxidised only
b. Reduced only
c. Proton acceptor only
d. Both oxidised and reduced
Answer : D

Question. In the reaction HAsO₂ + Sn²⁺ → As + Sn⁴⁺ + H₂O oxidising agent is:
a. Sn²⁺
b. Sn⁴⁺
c. As
d. HAsO₂
Answer : D

Question. HNO₂ acts both as reductant and oxidant, while HNO₃ acts only as oxidant. It is due to their:
a. Solubility ability
b. Maximum oxidation number
c. Minimum oxidation number
d. Minimum number of valence electrons
Answer : B

Question. Oxidation state of chlorine in perchloric acid is:
a. – 1
b. 0
c. – 7
d. + 7
Answer : D

Question. Oxidation number of carbon in H₂C₂O₄ is:
a. + 4
b. + 3
c. + 2
d. – 2
Answer : B

Question. The oxidation number of Fe and S in iron pyrites are:
a. 4, – 2
b. 2, – 1
c. 3, – 1.5
d. 3, – 1
Answer : A

Question. The oxidation states of the most electronegative element in the products of the reaction of BaO₂ with dilute H₂SO₄ are:
a. 0 and – 1
b. – 1 and – 2
c. – 2 and 0
d. – 2 and + 1
Answer : B

Question. Choose the correct option(s):
a. KClO₄ and KMnO₄ are isomorphous in nature
b. Equivalent weight of Fe_0.9O when it is converted to FeO is 332. (At wt. of Fe = 56)
c. Molar volume of water at STP is 22.4 litre
d. When ‘w’ g Na₂ SO₄ ⋅10H₂O is added in X g of water,molality of SO⁴⁻₂ is 1000/332X
Answer : A, B

Question. H₂O₂ Reduces K₄Fe (CN)₆:
a. In neutral solution
b. In acidic solution
c. In non-polar solvent
d. In alkaline solution
Answer : B

Question. SnCl₂ gives a precipitate with a solution of HgCl₂. In this process HgCl₂ is:
a. Reduced
b. Oxidised
c. Converted into a complex compound containing both Sn and Hg
d. Converted into a chloro complex of Hg
Answer : A

Question. In a reaction between zinc and iodine, in which zinc iodide is formed, what is being oxidised?
a. Zinc ions
b. Iodide ions
c. Zinc atom
d. Iodine
Answer : C

Question. Which of the following is redox reaction?
a. H₂SO₄ with NaOH
b. In atmosphere, O₃ from O₂ by lightning
c. Evaporation of H₂O
d. Nitrogen oxides form nitrogen and oxygen by lightning Disproportionation
Answer : D

Question. The oxidation number of Mn is +2 in:
a. Manganese oxide
b. Manganese chloride
c. Manganese sulphate
d. Potassium permanganate
Answer : A, B, C

Question. Oxygen has an oxidation state of –1 in:
a. H₂O₂
b. BaO₂
c. OF₂
d. H₂S₂O₈
Answer : A, B, D

Question. Cu₂S → Cu + 0 ; Equivalent weight of Cu₂ S = x₃
Cu₂S → Cu⁺ + S ; Equivalent weight of Cu₂ S = x₃
Cu₂S → Cu⁺ + S ; Equivalent weight of Cu₂ S = x₃
a. x₁ > x₂
b. x₂ > x₃
c. x₃ > x₁
d. x₃ > x₂
Answer : A, C, D

Question. Which reaction involves neither oxidation nor reduction?
(a) CrO42- → Cr2O72-
(b) Cr → CrCl3
(c) Na → Na+
(d) 2S2O32- → S4O62-
Answer : A

Question. The most powerful oxidizing agent from the following is
(a) H₃BO₃
(b) HPO₃
(c) H₃PO₄
(d) H₂SO₄
Answer : D

Question. Which one of the following reaction involves oxidation-reduction ?
(a) H₂ + Br₂ →2HBr
(b) NaBr + HCl → NaCl + HBr
(c) HBr + AgNO₃ →AgBr + HNO₃
(d) 2NaOH + H₂SO₄ → Na2SO₄ + 2H₂O
Answer : A

Question. Oxidation numbers of chlorine atoms in CaOCl₂ are
(a) 0, 0
(b) –1, –1
(c) –1, +1
(d) None of these
Answer : C

Question. In the reaction 3Br₂ + 6CO₃^2- + 3H₂O → 5Br- + BrO₃^- + 6HCO₃^-
(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
Answer : D

Question. Which of the following reactions depicts the oxidising property of SO₂ ?
(a) SO₂ + H₂O → H₂SO₃
(b) 2H₂S + SO₂ → 3S + 2H₂O
(c) Cl₂ + SO₂ → SO₂Cl₂
(d) 2MnO^-₄ + 5SO₂ + 2H₂O→ 5SO₄^2– + 2Mn²⁺ + 4H⁺
Answer : B

Question. E^Θ Values of some redox couples are given below. On the basis of these values choose the correct option.
E^Θ values : Br₂/Br ^– = + 1.90; Ag⁺ /Ag(s) = + 0.80 Cu²⁺ /Cu(s) = + 0.34; I₂(s) /I– = 0.54
(a) Cu will reduce Br^–
(b) Cu will reduce Ag
(c) Cu will reduce I^–
(d) Cu will reduce Br₂
Answer : D

Question. In the standardization of Na₂S₂O₃ using K₂Cr₂O₇ by iodometry, the equivalent weight of K₂ Cr₂ O₇ is
(a) Molecular weight/2
(b) Molecular weight/6
(c) Molecular weight/3
(d) Same as molecular weight
Answer : B

Question. The oxidation state of the most electronegative element in the products of the reaction between BaO₂ and H₂SO₄ are
(a) 0 and –1
(b) –1 and – 2
(c) – 2 and 0
(d) – 2 and + 1
Answer : B

Question. Which of the following substances acts as an oxidising as well as a reducing agent?
(a) Na₂O
(b) SnCl₂
(c) Na₂O₂
(d) NaNO₂
Answer : D

Question. Which of the following statements are correct concerning redox properties?
(i) A metal M for which E° for the half life reaction Mⁿ⁺ + ne^– ⇔ M is very negative will be a good reducing agent.
(ii) The oxidizing power of the halogens decreases from chlorine to iodine.
(iii) The reducing power of hydrogen halides increases from hydrogen chloride to hydrogen iodide
(a) (i), (ii) and (iii)
(b) (i) and (ii)
(c) (i) only
(d) (ii) and (iii)
Answer : A

Question. In the reaction Cr₂O₇^2- + 14H⁺ + 6I^- → 2Cr³⁺ + 7H₂O + 3I₂^- Which element is reduced
(a) I
(b) O
(c) H
(d) Cr
Answer : D

Question. Standard reduction electrode potentials of three metals A, B & C are respectively + 0.5 V, – 3.0 V & –1.2 V. The reducing powers of these metals are
(a) A > B > C
(b) C > B > A
(c) A > C > B
(d) B > C > A
Answer : D

Question. Which one of the following reactions involves disproportionation?
(a) 2H₂SO₄ + Cu → CuSO₄ + 2H₂O + SO₂
(b) As₂O₃ + 3H₂S → As₂S₃ + 3H₂O
(c) 2KOH + Cl₂ → KCl + KOCl + H₂O
(d) Ca₃P₂ + 6H₂O → 3Ca(OH)₂ + 2PH₃
Answer : V

Question. The formal oxidation numbers of Cr and Cl in the ions Cr₂O₇^2– and ClO₃^–, respectively are
(a) + 6 and +7
(b) +7 and +5
(c) +6 and +5
(d) +8 and +7
Answer : C

Match the Column

Question. Match the statement of Column with those in Column II:

a. A→ 2; B→ 3; C→ 4; D→ 1
b. A→ 3; B→ 1; C→ 2; D→ 4
c. A→ 3; B→ 4; C→ 2; D→ 1
d. A→ 2; B→ 3; C→ 1; D→ 4
Answer : C

Numeric Value Answer

Question. Atomic number of an element is 22. The highest O.S. exhibited by it in its compounds is
Answer : 4

Question. In the chemical reaction,
K₂Cr₂O₇ + XH₂SO₄ + YSO₂ → K₂SO₄ +Cr₂(SO₄)₃ + Z H₂O
X, Y and Z is
Answer : 5

Question. The O.N. of nitrogen in NO3¯ is
Answer : 5

Question. The number of electrons required to balance the following equation NO¯3 + 4H⁺ + e¯ → 2H₂ + O + NO is -
Answer : 3

Question. The oxidation state of iodine in H₄IO₆¯ is
Answer : 7