CBSE Class 11 Chemistry Redox Reactions Assignment

Question. The oxidation number of Cr in K₂Cr₂O₇ is:
a. +6
b. – 7
c. +2
d. – 2
Answer : A

Question. The oxidation state of nitrogen is highest in:
a. N₃H
b. NH₂OH
c. N₂H₄
d. NH₃
Answer : A

Question. What is the net charge on ferrous ion?
a. + 2
b. + 3
c. + 4
d. + 5
Answer : A

Question. When KMnO₄ is reduced with oxalic acid in acidic solution, the oxidation number of Mn changes from?
a. 7 to 4
b. 6 to 4
c. 7 to 2
d. 4 to 2
Answer : C

Question. The oxidation state of Mn in K₂MnO₄ :
a. + 2
b. + 7
c. – 2
d. + 6
Answer : D

Question. Oxidation number of nitrogen in NaNO₂ is:
a. + 2
b. + 3
c. + 4
d. – 3
Answer : B

Question. Oxidation number of cobalt in K[Co(CO)₄] is:
a. + 1
b. + 3
c. – 1
d. – 3
Answer : C

Question. In which compound, oxidation state of nitrogen is 1?
a. NO
b. N₂O
c. NH₂OH
d. N₂H₄
Answer : B

Question. The oxidation number and covalency of sulphur in the sulphur molecule (S₈) are respectively:
a. 0 and 2
b. 6 and 8
c. 0 and 8
d. 6 and 2
Answer : A

Question. In which of the following compound transition metal has zero oxidation state?
a. CrO₅
b. NH₂NH₂
c. NOClO₄
d. [Fe(CO)₅]
Answer : D

Question. The equivalent weight of phosphoric acid (H₃PO₄) in the reaction NaOH + H₃PO₄ → NaH₂PO₄ + H₂O is:
a. 25
b. 49
c. 59
d. 98
Answer : D

Question. What is the equivalent mass of 4 IO⁻₄ when it is converted into I₂ in acid medium?
a. M/6
b. M/7
c. M/5
d. M/4
Answer : B

Question. The oxidation state of nitrogen in N₃H is:
a. + 1/3
b. + 3
c. −1
d. − 1/3
Answer : D

Question. Sulphur has highest oxidation state in:
a. SO₂
b. H₂ SO₄
c. Na₂ S₂ O₃
d. Na₂ S₄ O₆
Answer : B

Question. An element which never has a positive oxidation number in any of its compounds:
a. Boron
b. Oxygen
c. Chlorine
d. Fluorine
Answer : D

Question. C₂H₂(g) + nO₂ → 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
Answer : B

Question. Starch paper is used to test for the presence of:
a. Iodine
b. Oxidising agent
c. Iodide ion
d. Reducing agent
Answer : A

Question. In the balanced chemical reaction, IO^-₃ + a_I^- + bH⁺ → cH₂O + dI₂ a, b, c and d respectively correspond to:
a. 5, 6, 3, 3
b. 5, 3, 6, 3
c. 3, 5, 3, 6
d. 5, 6, 5, 5
Answer : A

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

Question. To prevent rancidification of food material, which of the following is added?
a. Reducing agent
b. Anti-oxidant
c. Oxidising agent
d. None of these
Answer : B

Question. 15 g of KMnO₄ in acidic medium is equal to:
a. 0.09493 moles
b. 0.4446 g equivalents
c. 9.492 L of 0.05 N KMnO₄
d. 10 mL of 0.05 M KMnO₄
Answer : A, C

Question. In the equation H₂S + 2HNO₃ → 2H₂O + 2NO₂ + S
The equivalent weight of hydrogen sulphide is:
a. 16
b. 68
c. 34
d. 17
Answer : D

Question. The metal used in galvanizing of iron is:
a. Pb
b. Zn
c. Al
d. Sn
Answer : B

Question. Which one of the following nitrates will leave behind a metal on strong heating?
a. Ferric nitrate
b. Copper nitrate
c. Manganese nitrate
d. Silver nitrate
Answer : D

Question. The oxidation number of phosphorus vary from
(1) – 3 to + 5
(2) – 1 to + 1
(3) – 3 to + 3
(4) – 5 to + 1
Answer (1)

Question. White P reacts with caustic soda, the products are PH3 and NaH₂ PO ₂. The reaction is an example of
(1) Oxidation
(2) Reduction
(3) Disproportionation
(4) Neutralization
Answer (3)

Question. Oxidation number of oxygen atom in O₃ molecule is
(1) 0
(2) –2
(3) + 2
(4) – ½
Answer (1)

Question. Oxidation number of iodine varies from
(1) – 1 to + 1
(2) – 1 to + 7
(3) + 3 to + 5
(4) – 1 to + 5
Answer (2)

Question.The process in which oxidation number increases is
(1) Reduction
(2) Hydrolysis
(3) Oxidation
(4) Decomposition
Answer (3)

Question. The oxidation number of C in CH₄, CH₃Cl, CH₂Cl₂, CHCl₃and CCl ₄ is respectively
(1) –4, –2, 0, +2, +4
(2) +2, 4, 0, –2, –4
(3) 4, 2, 0, –2, 4
(4) 0, 2, –2, 4, 4
Answer (1)

Question. Chlorine is in +3 oxidation number in
(1) HCl
(2) HClO ₄
(3) ICl
(4) ClF₃
Answer (4)

Question. Given that the oxidation number of sulphur is –2, the equivalent weight of sulphur is
(1) 16
(2) 32
(3) 9
(4) 4
Answer (1)

Question.The brown ring complex compound is formulated as [Fe(H₂O)₅ NO]SO₄ . The oxidation state of iron is
(1) +1
(2) + 2
(3) + 3
(4) + 6
Answer (1)

Question.When iron is added to CuSO₄ solution, copper is precipitated. It is due to
(1) Oxidation of Cu⁺²
(2) Reduction of Cu⁺²
(3) Hydrolysis of CuSO₄
(4) Ionization of CuSO₄
Answer (2)

Question. Which one of the following is the correct match?
(1) Cl_2- only reducing agent
(2) HNO₂- only oxidising agent
(3) HNO₃- both oxidising and reducing agent
(4) SO₂- both oxidising and reducing agent
Answer (4)

Question. Oxidation number of sodium in sodium 3 amalgam is
(1) +1
(2) 0
(3) –1
(4) +2
Answer (2)

Question. In a reaction between zinc and iodine, zinc iodide is formed. Which is being oxidised?
(1) Zinc ions
(2) Iodide ions
(3) Zinc atom
(4) Iodine
Answer (3)

Question.Oxidation number of Cr in CrO ₅ is
(1) + 10
(2) + 6
(3) + 4
(4) + 5
Answer (2)

Question.In which of the following compounds, the oxidation number of iodine is fractional?
(1) IF₇
(2) I₃^–
(3) IF₅
(4) IF₃
Answer (2)

Question. Which of the following compound cannot be oxidised by O₃ ?
(1) KI
(2) KMnO₄
(3) K₂MnO₄
(4) FeSO₄
Answer (2)

Question.The oxidation number of sulphur in H₂S₂O₈ is
(1) + 7
(2) + 6
(3) – 6
(4) + 4
Answer (2)

ONE MARK QUESTIONS

1. What do you mean by oxidation number ?

2. Name a compound each in which hydrogen exists in i) +1 ii) -1 oxidation states

3. Define Redox couple.

4. Find the oxidation number of the element underlined 

a) Na₃VO₄     b) K₂CrO₄    c) CH₄    d) SO₂Cl₂   e) NO₂  f) BrF₃  g) Na₂S₄O₆  h) CH₂Cl₂  i) ClO₄-

TWO MARKS QUESTIONS

1. Name a compound each in which oxygen exists in i) +1 ii) -1 iii) +2 iv) -2 oxidation states

2. Define

i) stock notation

i) Standard electrode potential

3. Explain the following by giving example

i) Displacement redox reaction.

ii) Disproportionation reactions

4. Calculate the standard emf of the following cell at 298K using the standard electrode potential.

1 Determine the oxidation number of element underlined the following:
SiH₄ , BF₃ , BrO₄^- , C₂H₆ , Br₃O₈ , OF₂

2 Identify the oxidants and reductants in the given reaction :
(a) CH₄ + 4CL₂ → CCl₄ + 4HCL
(b) I₂ 2S₂O₃^2- → 2I- + S₄O₆^2-
(c) N₂H₄ + 2 H₂O₂ → N₂ + 4H₂O

3 Balance the following equations in basic medium by ion –electron method :
(1) P₄ + OH^- → PH₃ + H₂PO₂^-
(2) MnO₄^- + Fe²⁺ → MnO₂ + Fe³⁺
(3) CL₂O₇ + H₂O₂ → CLO₂^- + O₂

4 Balance the following equations in acidic medium by both method:
(1) MnO₄^- + C₂H₂O₄ → Mn²⁺ + CO₂
(2) H₂S + CL₂ → S + CL-
(3) MnO₄^- + C₂H₅OH → Mn²⁺ + CH₃COOH
(4) Cr₂O₇^2- + C₂O₄^2- → Cr³⁺ + CO₂

5 What is the most essential conditions that must be satisfied in redox reaction?

6 Arrange the molecules NH₃ , NO₂ , HN₃, NO₂^- , and N2H4 in deacreasing order of the oxidation state of nitrogen.

7 Explain the types of reactions with examples.

8 Define disproportionation reaction with two examples.

9 How would you know wheather a redox reaction is taking place in an acidic or alkaline medium?

10 What is the oxidation state of oxygen in water, hydrogenperoxide, oxygen gas and in oxyfluorides.