NEET Chemistry Redox Reactions MCQs Set A

Question: The process in which oxidation number increases is

• a) Reduction
• b) Hydrolysis
• c) Oxidation
• d) Decomposition

Answer: Oxidation

Question: The oxidation number of phosphorus vary from

• a) – 3 to + 5
• b) – 1 to + 1
• c) – 3 to + 3
• d) – 5 to + 1

Answer: – 3 to + 5

Question: Oxidation number of iodine varies from

• a) – 1 to + 1
• b) – 1 to + 7
• c) + 3 to + 5
• d) – 1 to + 5

Answer: – 1 to + 7

Question:  White P reacts with caustic soda, the products are PH₃ and NaH₂PO₂ . The reaction is an example of

• a) Oxidation
• b) Reduction
• c) Disproportionation
• d) Neutralization

Answer: Disproportionation

Question:  Oxidation number of oxygen atom in O₃ molecule is

• a) 0
• b) –2
• c) + 2
• d) – ½

Answer: 0

Question:  The oxidation number of C in CH₄, CH₃Cl, CH₂Cl₂, CHCl₃ and CCl₄ is respectively

• a) –4, –2, 0, +2, +4
• b) +2, 4, 0, –2, –4
• c) 4, 2, 0, –2, 4
• d) 0, 2, –2, 4, 4

Answer: –4, –2, 0, +2, +4

Question: Chlorine is in +3 oxidation number in

• a) HCl
• b) HClO₄
• c) ICl
• d) ClF₃

Answer:  ClF₃

Question: Given that the oxidation number of sulphur is –2, the equivalent weight of sulphur is

• a) 16
• b) 32
• c) 9
• d) 4

Answer: 16

Question: In a reaction between zinc and iodine, zinc iodide is formed. Which is being oxidised?

• a) Zinc ions
• b) Iodide ions
• c) Zinc atom
• d) Iodine

Answer: Zinc atom

Question:  In the following equation

• a) Bromine is oxidised and carbonate is reduced
• b) Bromine is reduced and carbonate is oxidised
• c) Bromine is neither reduced nor oxidised
• d) Bromine is reduced as well oxidised

Answer: Bromine is reduced as well oxidised

Question: In which reaction, there is change in oxidation number of N atom?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  When iron is added to CuSO₄ solution, copper is precipitated. It is due to

• a) Oxidation of Cu⁺²
• b) Reduction of Cu⁺²
• c) Hydrolysis of CuSO₄ 
• d) Ionization of CuSO₄

Answer:  Reduction of Cu⁺²

More Questions........................................................

Question: Which of the following reactions involves oxidation and reduction?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  The oxidation number of sulphur in H₂S₂O₈ is

• a) + 7
• b) + 6
• c) – 6
• d) + 4

Answer: + 6

Question: Which one of the following is the correct match?

• a) Cl₂- only reducing agent
• b) HNO₂- only oxidising agent
• c) HNO₃- both oxidising and reducing agent
• d) SO₂- both oxidising and reducing agent

Answer: SO₂- both oxidising and reducing agent

Question:  The brown ring complex compound is formulated as [Fe(H₂O)₅NO]SO₄ . The oxidation state of iron is

• a) +1
• b) + 2
• c) + 3
• d) + 6

Answer: +1

Question: Phosphorus has the oxidation state + 3 in

• a) Orthophosphoricacid    (H₃PO₄)  
• b) Phosphorus acid    (H₃PO₃)
• c) Metaphosphoric acid    (HPO₃) 
• d) Pyrophosphoric acid    (H₄P₂O₇)

Answer: Phosphorus acid    (H₃PO₃)

Question: Given that the oxidation number of sulphur is –2, the equivalent weight of sulphur is

• a) 16
• b) 32
• c) 9
• d) 4

Answer: 16

Question:  Oxidation number of Cr in CrO₅  is

• a) + 10
• b) + 6
• c) + 4
• d) + 5

Answer: + 6

Question: In which of the following compounds iron has lowest oxidation number?

• a) FeSO₄· (NH₄)₂SO₄· 6H₂O 
• b) K₄[Fe(CN)₆] 
• c) Fe₂O
• d) Fe₂O₃

Answer: Fe₂O

Question: In which of the following compounds, the oxidation number of iodine is fractional?

• a) IF₇
• b) I₃^–
• c) IF₅
• d) IF₃

Answer: I₃^–

Question: Which reaction involves neither oxidation nor reduction?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  In the chemical reaction,

a, b and c are

• a) 1, 3, 1
• b) 4, 1, 4
• c) 3, 2, 3
• d) 2, 1, 2

Answer: 1, 3, 1

Question: Oxidation number of sodium in sodium 3 amalgam is

• a) +1
• b) 0
• c) –1
• d) +2

Answer: 0

Question:  Which of the following compound cannot be oxidised by O₃?

• a) KI
• b) KMnO₄
• c) K₂MnO₄ 
• d) FeSO₄

Answer: KMnO₄

Question:  In alkaline solution KMnO₄ reacts as follows

Therefore, its equivalent weight will be

• a) 31.6
• b) 52.7
• c) 79.0
• d) 158.0

Answer: 158.0

Question:  The equivalent weight of FeS₂ in the following reaction is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  When SO₂ is passed in acidified potassium dichromate solution, the oxidation number of S is changed from

• a) + 4 to zero
• b) + 4 to + 2
• c) + 4 to + 6
• d) + 6 to + 4

Answer: + 4 to + 6

Question:  How many mole of FeSO₄ reacted with one mole of KMnO₄ in acidic medium?

• a)

  

• b) 5
• c)

  

• d)

  

Answer: 5

Question: A compound of Xe and F is found to have 53.3% Xe (At. mass = 133). Oxidation number of Xe in this compound is

• a) +2
• b) 0
• c) +4
• d) +6

Answer: +6

Question: Which of the following is not correct for electrochemical cell?

• a) Convert chemical energy to electrical energy
• b) Anode is –ve terminal
• c) Cathode is –ve terminal
• d) Cathode is +ve terminal

Answer: Cathode is –ve terminal

Question: Which of the following is not a redox reaction?

• a)

  

• b)

  

• c) Photosynthesis
• d) Cell respiration

Answer:

Question: Redox reaction have no concern with

• a) Neutralization of acid bases
• b) Salt hydrolysis
• c) Esterification
• d) All of these

Answer: All of these

Question: In the process of photosynthesis, which takes place in green plants which undergoes reduction?

• a) Water
• b) CO₂  
• c) Protons
• d) Photons

Answer:  CO₂

Question:

n factor of nitrobenzene in this process

• a) 3
• b) 6
• c) 2
• d) 4

Answer: 6

Question:  The ratio of number of moles of KMnO₄ and K₂Cr₂O₇ required to oxidise 0.1 mol Sn²⁺ to Sn⁺⁴ in acidic medium

• a) 6 : 5
• b) 5 : 6
• c) 1 : 2
• d) 2 : 1

Answer: 5 : 6

Question:

The equivalent mass of Cl₂ in the above reaction is

• a) M
• b)

  

• c)

  

• d)

  

Answer:

Question: KCl is used as an electrolyte in salt bridge because

• a) K⁺ and Cl^– are isoelectronic 
• b) Monovalent ions are required
• c) Both the ions have almost same velocity
• d) They are having similar size

Answer: Both the ions have almost same velocity

Question: Electrode potential depends upon

• a) Size of electrode
• b) Surface area of electrode
• c) Temperature
• d) Shape of electrode

Answer: Temperature

Question:  EMF of the given cell

• a) 2.8 V
• b) 1.8 V
• c) 0 V
• d) –1.8 V

Answer: 2.8 V

Question:  Oxidation number of Cr atom in CrO₅ and K₃CrO₈ respectively

• a) +6, +6
• b) +5, +6
• c) +6, +5
• d) +5, +5

Answer: +6, +5

Question:  Number of electrons involved in the reaction when 0.1 mol NH₃ dissolved in water

• a) 2
• b) 0.4
• c) 0.9
• d) Zero

Answer: Zero

Question:

Electrode potential for given reaction

• a) 3.02 V
• b) 6.04 V
• c) 1.5 V
• d) –3.02 V

Answer: 3.02 V

Question: Three metals A, B and C are arranged in increasing order of standard reduction electrode potential, hence their chemical reactivity order will be

• a) A < B < C
• b) A > B > C
• c) B > C > A
• d) A = B = C

Answer: A > B > C

Question: Find the incorrect statement

• a) Higher reduction potential of non-metal means stronger reducing agent
• b) Lower oxidation potential of a metal means strong oxidising agent
• c) Oxidation state of oxygen in O₃ is –1
• d) All of these

Answer: All of these

Question: When an alkali metal is reacted with hydrogen then metallic hydride is formed. In this reaction

• a) Hydrogen is oxidised
• b) Hydrogen is reduced
• c) Hydrogen is neither oxidised nor reduced
• d) Hydrogen is oxidised as well as reduced

Answer: Hydrogen is reduced

Question:  In case of CH₃COOH, the oxidation number of carbon of carboxylic group is

• a) –3
• b) Zero
• c) +1
• d) +3

Answer: +3

Question:  How many moles of KMnO₄ are required to oxidise one mole of SnCl₂ in acidic medium?

• a) 1/5
• b) 2/5
• c) 3/5
• d) 4/5

Answer: 2/5

Question: Which compound acts as oxidising agent only?

• a) SO₂
• b) H₂S
• c) H₂SO₄
• d) HNO₂

Answer: H₂SO₄

Question: The average oxidation state of chlorine in bleaching powder is

• a) –1
• b) +1
• c) Zero
• d) –2 as well as +2

Answer: Zero

Question: When benzaldehyde is oxidised to give benzoic acid then the oxidation state of carbon of aldehydic group is changed from

• a) +2 to +3
• b) +1 to +3
• c) Zero to +2
• d) No change

Answer: +1 to +3

Question: Which of the following is incorrect regarding salt bridge solution?

• a) Solution must be a strong electrolyte
• b) Solution should be inert towards both electrodes
• c) Size of cations and anions of salt should be much different
• d) Salt bridge solution is prepared in gelatin or agar-agar to make it semi-solid

Answer: Size of cations and anions of salt should be much different

Question:  Standard electrode potentials of redox couples A²⁺/A, B²⁺/B, C/C²⁺ and D²⁺/D are 0.3 V, –0.5 V, –0.75 V and 0.9 V 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

Answer: D²⁺/D and B²⁺/B 

Question:  The number of moles of H₂O₂ required to completely react with 400 ml of 0.5 N KMnO₄ in acidic medium are

• a) 0.1
• b) 0.2
• c) 1.0
• d) 0.5

Answer: 0.1

Question:

The coefficient X, Y and Z are

• a) 6, 2, 2
• b) 5, 1, 3
• c) 12, 2, 6
• d) 12, 1, 6

Answer: 12, 2, 6

Question: Which of the following processes does not involve oxidation of iron?

• a) Liberation of H₂ from steam by iron at high temperature  
• b) Rusting of iron sheets
• c) Decolourization of blue CuSO₄ solution by iron
• d) Formation of Fe(CO)₅ from Fe

Answer:   Formation of Fe(CO)₅ from Fe

Question:

Role of hydrogen peroxide in the above reactions is respectively 

• a) Oxidizing in (a) and reducing in
• b) Reducing in (a) and oxidizing in (b)
• c) Reducing in (a) and (b)
• d) Oxidizing in (a) and (b)

Answer: Reducing in (a) and (b)

Question: In which of the following compounds, nitrogen exhibits highest oxidation state?

• a) N₃H
• b) NH₂OH
• c) N₂H₄
• d) NH₃

Answer: N₃H

Question:  Oxidation states of P in H₄P₂O₅, H₄P₂O₆, H₄P₂O₇ are respectively 

• a) +3, +5, +4
• b) +5, +3, +4
• c) +5, +4, +3
• d) +3, +4, +5

Answer: +3, +4, +5

Question:  Oxidation numbers of P in 

 are respectively

• a) + 3, + 6 and + 5
• b) + 5, + 3 and + 6
• c) – 3, + 6 and + 6
• d) + 5, + 6 and + 6

Answer: + 5, + 6 and + 6