Here below some basic MCQ’s about “Oxidation and Reduction” with answer which is explained in details. Let’s check one by one.
Question 1:
Which of the following processes represents oxidation?
A) Fe2+→Fe3++e−Fe2+→Fe3++e−
B) Cu2++2e−→CuCu2++2e−→Cu
C) O2+4e−+4H+→2H2OO2+4e−+4H+→2H2O
D) H2→2H++2e−H2→2H++2e−
Answer: A) Fe2+→Fe3++e−Fe2+→Fe3++e−
Explanation: Oxidation is defined as the loss of electrons. In option A, iron (II) loses an electron to become iron (III).
Question 2:
In the reaction 2H2+O2→2H2O2H2+O2→2H2O, which substance is reduced?
A) H2H2
B) O2O2
C) H2OH2O
D) None of the above
Answer: B) O2O2
Explanation: Reduction is the gain of electrons. Oxygen in this reaction gains electrons (it goes from 0 in O2O2 to -2 in H2OH2O).
Question 3:
Identify the reducing agent in the reaction 2Na+Cl2→2NaCl2Na+Cl2→2NaCl.
A) NaNa
B) Cl2Cl2
C) NaClNaCl
D) None of the above
Answer: A) NaNa
Explanation: The reducing agent is the substance that donates electrons and is oxidized in the process. Sodium is oxidized from 0 to +1.
Question 4:
Which of the following statements is true regarding oxidation and reduction?
A) Oxidation involves gain of electrons.
B) Reduction involves loss of electrons.
C) Oxidation and reduction can occur simultaneously.
D) None of the above.
Answer: C) Oxidation and reduction can occur simultaneously.
Explanation: Oxidation and reduction always occur together in a redox reaction; when one substance is oxidized, another must be reduced.
Question 5:
In which of the following reactions is sulfur being oxidized?
A) S+O2→SO2S+O2→SO2
B) SO2+H2O→H2SO4SO2+H2O→H2SO4
C) H2S→S+H2H2S→S+H2
D) 2S+3O2→2SO32S+3O2→2SO3
Answer: D) 2S+3O2→2SO32S+3O2→2SO3
Explanation: In this reaction, sulfur goes from 0 in elemental form to +6 in SO3SO3, indicating it is being oxidized.
Question 6:
What is the oxidation state of sulfur in H2SO4H2SO4?
A) +4
B) +6
C) -2
D) 0
Answer: B) +6
Explanation: In H2SO4H2SO4, the oxidation state of sulfur is +6, calculated as follows: 2(+1)+x+4(−2)=02(+1)+x+4(−2)=0 leads to x=+6x=+6.
Question 7:
Which of the following is a characteristic of a reducing agent?
A) It is oxidized in the reaction.
B) It gains electrons.
C) It is reduced in the reaction.
D) None of the above.
Answer: A) It is oxidized in the reaction.
Explanation: A reducing agent donates electrons and, in doing so, becomes oxidized itself.
Question 8:
In the reaction Zn+Cu2+→Zn2++CuZn+Cu2+→Zn2++Cu, what is oxidized?
A) ZnZn
B) Cu2+Cu2+
C) Zn2+Zn2+
D) CuCu
Answer: A) ZnZn
Explanation: Zinc is oxidized as it loses electrons to become Zn2+Zn2+.
Question 9:
What is the product of the reduction of MnO4−MnO4− in an acidic solution?
A) MnO2MnO2
B) Mn2+Mn2+
C) Mn2O7Mn2O7
D) MnO42−MnO42−
Answer: B) Mn2+Mn2+
Explanation: In acidic conditions, permanganate ions MnO4−MnO4− are reduced to Mn2+Mn2+.
Question 10:
Which of the following represents a redox reaction?
A) H2+Cl2→2HClH2+Cl2→2HCl
B) 2Na+2H2O→2NaOH+H22Na+2H2O→2NaOH+H2
C) CaCO3→CaO+CO2CaCO3→CaO+CO2
D) NaCl→Na+Cl2NaCl→Na+Cl2
Answer: B) 2Na+2H2O→2NaOH+H22Na+2H2O→2NaOH+H2
Explanation: In this reaction, sodium is oxidized (loses electrons) and water is reduced (gains electrons).
Question 11:
What is the oxidation state of chlorine in NaClO3NaClO3?
A) +1
B) +3
C) +5
D) +7
Answer: B) +5
Explanation: In NaClO3NaClO3, the oxidation state of chlorine can be calculated as follows: (+1)+x+3(−2)=0(+1)+x+3(−2)=0 leads to x=+5x=+5.
Question 12:
In the reaction Fe3++3e−→FeFe3++3e−→Fe, what is happening?
A) Oxidation
B) Reduction
C) Precipitation
D) Ionization
Answer: B) Reduction
Explanation: Iron (III) is gaining electrons to become elemental iron, which is a reduction process.
Question 13:
Which of the following compounds can act as a strong oxidizing agent?
A) H2OH2O
B) KClKCl
C) KMnO4KMnO4
D) NaClNaCl
Answer: C) KMnO4KMnO4
Explanation: Potassium permanganate (KMnO4KMnO4) is a well-known strong oxidizing agent.
Question 14:
In a galvanic cell, which electrode is the site of reduction?
A) Anode
B) Cathode
C) Salt bridge
D) None of the above
Answer: B) Cathode
Explanation: In a galvanic cell, reduction occurs at the cathode, while oxidation occurs at the anode.
Question 15:
What happens to the oxidation state of an element that is reduced?
A) It increases.
B) It decreases.
C) It remains the same.
D) It cannot be determined.
Answer: B) It decreases.
Explanation: Reduction involves the gain of electrons, which decreases the oxidation state of the element.
Question 16:
In the reaction 2Fe2O3+3C→4Fe+3CO22Fe2O3+3C→4Fe+3CO2, what role does carbon play?
A) Oxidizing agent
B) Reducing agent
C) Catalyst
D) None of the above
Answer: B) Reducing agent
Explanation: Carbon is oxidized to carbon dioxide, thus it acts as a reducing agent by donating electrons to iron(III) oxide.
Question 17:
What is the oxidation state of nitrogen in NH3NH3?
A) +1
B) -1
C) -3
D) 0
Answer: C) -3
Explanation: In ammonia (NH3NH3), nitrogen has an oxidation state of -3.
Question 18:
Which of the following is an example of a disproportionation reaction?
A) 2H2+O2→2H2O2H2+O2→2H2O
B) 2Cu+→Cu+Cu2+2Cu+→Cu+Cu2+
C) Zn+Cu2+→Zn2++CuZn+Cu2+→Zn2++Cu
D) Cl2+2Na→2NaClCl2+2Na→2NaCl
Answer: B) 2Cu+→Cu+Cu2+2Cu+→Cu+Cu2+
Explanation: In this reaction, Cu+Cu+ is both oxidized and reduced, making it a disproportionation reaction.
Question 19:
What is the oxidation state of phosphorus in H3PO4H3PO4?
A) +3
B) +5
C) +1
D) +7
Answer: B) +5
Explanation: In phosphoric acid (H3PO4H3PO4), the oxidation state of phosphorus is +5.
Question 20:
Which of the following ions can act as an oxidizing agent?
A) Fe3+Fe3+
B) Na+Na+
C) Ca2+Ca2+
D) Li+Li+
Answer: A) Fe3+Fe3+
Explanation: Fe3+Fe3+ can gain electrons to be reduced to Fe2+Fe2+, making it an oxidizing agent.
Question 21:
In which of the following reactions does the oxidation state of iron decrease?
A) Fe2O3+3CO→2Fe+3CO2Fe2O3+3CO→2Fe+3CO2
B) 4Fe+3O2→2Fe2O34Fe+3O2→2Fe2O3
C) Fe+Cl2→FeCl2Fe+Cl2→FeCl2
D) Fe3++3e−→FeFe3++3e−→Fe
Answer: D) Fe3++3e−→FeFe3++3e−→Fe
Explanation: In this reaction, iron’s oxidation state decreases from +3 to 0, indicating reduction.
Question 22:
In a redox reaction, which species undergoes oxidation?
A) The species that gains electrons.
B) The species that loses electrons.
C) The species that remains unchanged.
D) None of the above.
Answer: B) The species that loses electrons.
Explanation: Oxidation is characterized by the loss of electrons.
Question 23:
In the reaction 4Al+3O2→2Al2O34Al+3O2→2Al2O3, which element is oxidized?
A) Al
B) O
C) Al2O3Al2O3
D) None of the above
Answer: A) Al
Explanation: Aluminum is oxidized from 0 in elemental form to +3 in Al2O3Al2O3.
Question 24:
Which of the following can act as both an oxidizing and reducing agent?
A) H2OH2O
B) H2O2H2O2
C) Cl2Cl2
D) SO2SO2
Answer: B) H2O2H2O2
Explanation: Hydrogen peroxide (H2O2H2O2) can act as an oxidizing agent by accepting electrons or as a reducing agent by donating electrons.
Question 25:
What is the oxidation state of manganese in MnO4−MnO4−?
A) +4
B) +6
C) +7
D) +2
Answer: C) +7
Explanation: In permanganate ion MnO4−MnO4−, the oxidation state of manganese is +7, calculated as follows: x+4(−2)=−1x+4(−2)=−1 leads to x=+7x=+7.
Question 26:
Which of the following is a strong reducing agent?
A) H2OH2O
B) NaNa
C) Cl2Cl2
D) H2O2H2O2
Answer: B) NaNa
Explanation: Sodium is a strong reducing agent because it readily loses electrons to form Na+Na+.
Question 27:
In the reaction 2Mg+O2→2MgO2Mg+O2→2MgO, which element is reduced?
A) Mg
B) O
C) Both Mg and O
D) None of the above
Answer: B) O
Explanation: Oxygen is reduced as it gains electrons to go from 0 in O2O2 to -2 in MgOMgO.
Question 28:
What is the oxidation state of chromium in Cr2O72−Cr2O72−?
A) +3
B) +4
C) +6
D) +2
Answer: C) +6
Explanation: In dichromate ion Cr2O72−Cr2O72−, the oxidation state of chromium is +6, calculated as follows: 2x+7(−2)=−22x+7(−2)=−2 leads to x=+6x=+6.
Question 29:
In the reaction 2H2+O2→2H2O2H2+O2→2H2O, what is the reducing agent?
A) H2H2
B) O2O2
C) H2OH2O
D) None of the above
Answer: A) H2H2
Explanation: Hydrogen gas H2H2 donates electrons and is oxidized, thus acting as the reducing agent.
Question 30:
Which of the following changes represents a reduction?
A) Cu2++2e−→CuCu2++2e−→Cu
B) Ag→Ag++e−Ag→Ag++e−
C) Fe3+→Fe2++e−Fe3+→Fe2++e−
D) Cl−→Cl2+2e−Cl−→Cl2+2e−
Answer: A) Cu2++2e−→CuCu2++2e−→Cu
Explanation: This reaction shows the gain of electrons by copper ions, indicating a reduction process.
Question 31:
What is the oxidation state of carbon in CH4CH4?
A) -4
B) +4
C) 0
D) +2
Answer: A) -4
Explanation: In methane (CH4CH4), the oxidation state of carbon is -4, as it is bonded to hydrogen atoms that have an oxidation state of +1.
Question 32:
Which of the following represents an oxidation reaction?
A) Fe3++3e−→FeFe3++3e−→Fe
B) Mg+Cl2→MgCl2Mg+Cl2→MgCl2
C) Cu+2e−→Cu2+Cu+2e−→Cu2+
D) H2+2e−→2H−H2+2e−→2H−
Answer: C) Cu+2e−→Cu2+Cu+2e−→Cu2+
Explanation: Copper is losing electrons and increasing its oxidation state from 0 to +2, which is oxidation.
Question 33:
In a redox reaction, which of the following pairs are always oxidizing and reducing agents, respectively?
A) Fe3+Fe3+ and CuCu
B) AgAg and AuAu
C) Cl−Cl− and Br2Br2
D) NaNa and MgMg
Answer: C) Cl−Cl− and Br2Br2
Explanation: In this case, Cl−Cl− acts as a reducing agent, while Br2Br2 acts as an oxidizing agent in the redox reaction.
Question 34:
Which of the following species is commonly used as an oxidizing agent in organic reactions?
A) H2O2H2O2
B) NaClNaCl
C) NaOHNaOH
D) H2H2
Answer: A) H2O2H2O2
Explanation: Hydrogen peroxide is frequently used as an oxidizing agent in various organic reactions.
Question 35:
In the balanced reaction 2Fe+3Cl2→2FeCl32Fe+3Cl2→2FeCl3, which element is oxidized?
A) Cl
B) Fe
C) FeCl
D) None of the above
Answer: B) Fe
Explanation: Iron (Fe) is oxidized from 0 to +3 in FeCl3FeCl3.
Question 36:
Which ion is reduced in the reaction 2MnO4−+5C2O42−+6H+→2Mn2++10CO2+3H2O2MnO4−+5C2O42−+6H+→2Mn2++10CO2+3H2O?
A) MnO4−MnO4−
B) C2O42−C2O42−
C) H+H+
D) CO2CO2
Answer: A) MnO4−MnO4−
Explanation: Manganese in MnO4−MnO4− is reduced to Mn2+Mn2+, going from +7 to +2 oxidation state.
Question 37:
What is the oxidation state of sulfur in H2SH2S?
A) +2
B) -2
C) 0
D) +1
Answer: B) -2
Explanation: In hydrogen sulfide (H2SH2S), sulfur has an oxidation state of -2.
Question 38:
Which of the following is a common oxidizing agent used in organic chemistry?
A) KMnO4KMnO4
B) NaClNaCl
C) HClHCl
D) CaCO3CaCO3
Answer: A) KMnO4KMnO4
Explanation: Potassium permanganate (KMnO4KMnO4) is widely used as an oxidizing agent in organic chemistry.
Question 39:
In the reaction 2H2+O2→2H2O2H2+O2→2H2O, what is the oxidation state of oxygen in water?
A) -2
B) 0
C) +1
D) -1
Answer: A) -2
Explanation: In water (H2OH2O), the oxidation state of oxygen is -2.
Question 40:
What is the primary role of a salt bridge in an electrochemical cell?
A) To provide a source of electrons.
B) To maintain charge balance.
C) To promote oxidation.
D) To prevent oxidation.
Answer: B) To maintain charge balance.
Explanation: A salt bridge allows the movement of ions, helping to maintain electrical neutrality in the half-cells.
Question 41:
In the reaction H2+F2→2HFH2+F2→2HF, which species is oxidized?
A) H2H2
B) F2F2
C) HFHF
D) None of the above
Answer: A) H2H2
Explanation: Hydrogen is oxidized as it goes from 0 in H2H2 to +1 in HFHF.
Question 42:
Which of the following is the correct definition of oxidation?
A) Gain of protons.
B) Loss of neutrons.
C) Loss of electrons.
D) Gain of electrons.
Answer: C) Loss of electrons.
Explanation: Oxidation is defined as the loss of electrons, which increases the oxidation state.
Question 43:
In the reaction 2Ag++Cu→2Ag+Cu2+2Ag++Cu→2Ag+Cu2+, which species acts as the reducing agent?
A) Ag+Ag+
B) CuCu
C) AgAg
D) Cu2+Cu2+
Answer: B) CuCu
Explanation: Copper is oxidized and acts as the reducing agent by donating electrons to silver ions.
Question 44:
What is the oxidation state of chlorine in Cl2Cl2?
A) +1
B) 0
C) -1
D) +2
Answer: B) 0
Explanation: In elemental form, the oxidation state of chlorine is 0.
Question 45:
Which of the following describes a reduction reaction?
A) Zn2++2e−→ZnZn2++2e−→Zn
B) H2+2e−→2H−H2+2e−→2H−
C) O2+4e−→2O2−O2+4e−→2O2−
D) All of the above
Answer: D) All of the above
Explanation: Each of the reactions shows a gain of electrons, which is the definition of reduction.
Question 46:
In which of the following compounds does sulfur have an oxidation state of +4?
A) SO2SO2
B) H2SH2S
C) SO3SO3
D) S8S8
Answer: A) SO2SO2
Explanation: In sulfur dioxide (SO2SO2), sulfur has an oxidation state of +4.
Question 47:
Which reaction represents a redox process?
A) NaOH+HCl→NaCl+H2ONaOH+HCl→NaCl+H2O
B) CaCO3→CaO+CO2CaCO3→CaO+CO2
C) Fe3++3e−→FeFe3++3e−→Fe
D) H2+Cl2→2HClH2+Cl2→2HCl
Answer: C) Fe3++3e−→FeFe3++3e−→Fe
Explanation: This reaction involves a change in oxidation states, showing that it is a redox process.
Question 48:
In the reaction 4Al+3O2→2Al2O34Al+3O2→2Al2O3, which substance is reduced?
A) Al
B) O
C) Al2O3Al2O3
D) None of the above
Answer: B) O
Explanation: Oxygen is reduced from 0 in O2O2 to -2 in Al2O3Al2O3.
Question 49:
What is the oxidation state of nitrogen in NO3−NO3−?
A) +1
B) +3
C) +5
D) +4
Answer: C) +5
Explanation: In the nitrate ion (NO3−NO3−), nitrogen has an oxidation state of +5.
Question 50:
Which of the following is a common characteristic of both oxidation and reduction reactions?
A) They involve the transfer of electrons.
B) They occur independently of each other.
C) They always produce a gas.
D) None of the above.
Answer: A) They involve the transfer of electrons.
Explanation: Oxidation and reduction are always coupled processes involving electron transfer.
Question 51:
Which of the following is a characteristic of oxidation?
A) Gain of electrons
B) Loss of hydrogen
C) Gain of oxygen
D) Both B and C
Answer: D) Both B and C
Explanation: Oxidation can involve both the loss of hydrogen and the gain of oxygen.
Question 52:
In the reaction 2FeCl3+Sn→2FeCl2+SnCl22FeCl3+Sn→2FeCl2+SnCl2, which species is reduced?
A) FeCl3FeCl3
B) FeCl2FeCl2
C) SnSn
D) SnCl2SnCl2
Answer: A) FeCl3FeCl3
Explanation: Iron in FeCl3FeCl3 is reduced from +3 to +2 in FeCl2FeCl2.
Question 53:
Which element has the highest oxidation state in K2Cr2O7K2Cr2O7?
A) K
B) Cr
C) O
D) None of the above
Answer: B) Cr
Explanation: In potassium dichromate (K2Cr2O7K2Cr2O7), chromium has an oxidation state of +6.
Question 54:
What is the oxidation state of phosphorus in H3PO2H3PO2?
A) +1
B) +3
C) +5
D) 0
Answer: B) +3
Explanation: In phosphorous acid (H3PO2H3PO2), phosphorus has an oxidation state of +3.
Question 55:
Which of the following compounds is a common reducing agent?
A) H2O2H2O2
B) Fe3+Fe3+
C) NaNa
D) Cl2Cl2
Answer: C) NaNa
Explanation: Sodium is a strong reducing agent because it readily donates electrons.
Question 56:
In the reaction 2H2+O2→2H2O2H2+O2→2H2O, what is the change in oxidation state of oxygen?
A) 0 to -1
B) 0 to -2
C) +1 to -2
D) 0 to +1
Answer: B) 0 to -2
Explanation: Oxygen is reduced as it goes from 0 in O2O2 to -2 in H2OH2O.
Question 57:
In a galvanic cell, the anode is the site of:
A) Reduction
B) Oxidation
C) Neutralization
D) Electrolysis
Answer: B) Oxidation
Explanation: The anode is where oxidation occurs in a galvanic cell.
Question 58:
Which of the following is an example of a redox reaction?
A) 2Na+Cl2→2NaCl2Na+Cl2→2NaCl
B) HCl+NaOH→NaCl+H2OHCl+NaOH→NaCl+H2O
C) CaCO3→CaO+CO2CaCO3→CaO+CO2
D) H2+O2→H2OH2+O2→H2O
Answer: A) 2Na+Cl2→2NaCl2Na+Cl2→2NaCl
Explanation: Sodium is oxidized and chlorine is reduced in this reaction, indicating it is a redox reaction.
Question 59:
What is the oxidation state of sulfur in H2SO3H2SO3?
A) +4
B) +6
C) -2
D) 0
Answer: A) +4
Explanation: In sulfurous acid (H2SO3H2SO3), sulfur has an oxidation state of +4.
Question 60:
Which of the following ions is the strongest oxidizing agent?
A) Fe3+Fe3+
B) Cl−Cl−
C) MnO4−MnO4−
D) I−I−
Answer: C) MnO4−MnO4−
Explanation: The permanganate ion is a strong oxidizing agent, particularly in acidic solutions.
Question 61:
In the reaction Zn+Cu2+→Zn2++CuZn+Cu2+→Zn2++Cu, which species is oxidized?
A) ZnZn
B) Cu2+Cu2+
C) CuCu
D) Zn2+Zn2+
Answer: A) ZnZn
Explanation: Zinc is oxidized as it loses electrons to become Zn2+Zn2+.
Question 62:
Which of the following species is oxidized in the reaction 2MnO4−+5C2O42−+6H+→2Mn2++10CO2+3H2O2MnO4−+5C2O42−+6H+→2Mn2++10CO2+3H2O?
A) C2O42−C2O42−
B) MnO4−MnO4−
C) H+H+
D) CO2CO2
Answer: A) C2O42−C2O42−
Explanation: The oxalate ion C2O42−C2O42− is oxidized to CO2CO2.
Question 63:
In the electrochemical series, which of the following metals is the best reducing agent?
A) AuAu
B) AgAg
C) LiLi
D) CuCu
Answer: C) LiLi
Explanation: Lithium is a strong reducing agent because it has a high tendency to lose electrons.
Question 64:
What is the oxidation state of chromium in CrO42−CrO42−?
A) +2
B) +3
C) +4
D) +6
Answer: D) +6
Explanation: In the chromate ion CrO42−CrO42−, chromium has an oxidation state of +6.
Question 65:
Which of the following represents a reduction reaction?
A) Na→Na++e−Na→Na++e−
B) Cl+e−→Cl−Cl+e−→Cl−
C) Fe3+→FeFe3+→Fe
D) Both B and C
Answer: D) Both B and C
Explanation: Both reactions show a gain of electrons, indicating reduction.
Question 66:
Which of the following ions is most likely to undergo reduction?
A) Ca2+Ca2+
B) Mg2+Mg2+
C) Ag+Ag+
D) K+K+
Answer: C) Ag+Ag+
Explanation: Silver ion Ag+Ag+ can easily gain an electron to become elemental silver, indicating it is likely to undergo reduction.
Question 67:
What happens to the oxidation state of an element during oxidation?
A) It decreases.
B) It increases.
C) It remains the same.
D) It becomes negative.
Answer: B) It increases.
Explanation: During oxidation, an element loses electrons, resulting in an increase in its oxidation state.
Question 68:
In the reaction 2Na+Cl2→2NaCl2Na+Cl2→2NaCl, what is the oxidation state of sodium in NaClNaCl?
A) +1
B) 0
C) -1
D) +2
Answer: A) +1
Explanation: In sodium chloride (NaClNaCl), sodium has an oxidation state of +1.
Question 69:
In which of the following reactions is sulfur both oxidized and reduced?
A) 2S+3O2→2SO32S+3O2→2SO3
B) 2H2S→2S+2H22H2S→2S+2H2
C) 2SO2+O2→2SO32SO2+O2→2SO3
D) 4H2+S→2H2S4H2+S→2H2S
Answer: B) 2H2S→2S+2H22H2S→2S+2H2
Explanation: In this reaction, sulfur in hydrogen sulfide is oxidized to elemental sulfur and also reduced in the process of formation of hydrogen.
Question 70:
What is the oxidation state of nitrogen in NH4+NH4+?
A) -3
B) +3
C) +1
D) 0
Answer: A) -3
Explanation: In ammonium ion (NH4+NH4+), nitrogen has an oxidation state of -3.
Question 71:
In which of the following does chlorine have an oxidation state of +1?
A) Cl2Cl2
B) HClOHClO
C) ClO2ClO2
D) Cl2OCl2O
Answer: B) HClOHClO
Explanation: In hypochlorous acid (HClOHClO), chlorine has an oxidation state of +1.
Question 72:
Which process is an example of a disproportionation reaction?
A) 2H2+O2→2H2O2H2+O2→2H2O
B) 2Ag++Cu→2Ag+Cu2+2Ag++Cu→2Ag+Cu2+
C) 2H2O2→2H2O+O22H2O2→2H2O+O2
D) NaCl→Na++Cl−NaCl→Na++Cl−
Answer: C) 2H2O2→2H2O+O22H2O2→2H2O+O2
Explanation: In this reaction, oxygen in hydrogen peroxide is both oxidized and reduced.
Question 73:
What is the oxidation state of phosphorus in PCl5PCl5?
A) +3
B) +5
C) 0
D) -5
Answer: B) +5
Explanation: In phosphorus pentachloride (PCl5PCl5), phosphorus has an oxidation state of +5.
Question 74:
Which of the following reactions involves an increase in oxidation state?
A) Fe3++3e−→FeFe3++3e−→Fe
B) H2+2e−→2H−H2+2e−→2H−
C) Ag++e−→AgAg++e−→Ag
D) Cu+2Ag+→2Ag+Cu2+Cu+2Ag+→2Ag+Cu2+
Answer: D) Cu+2Ag+→2Ag+Cu2+Cu+2Ag+→2Ag+Cu2+
Explanation: Copper is oxidized from 0 to +2, indicating an increase in oxidation state.
Question 75:
What is the oxidation state of nitrogen in N2O4N2O4?
A) +4
B) +2
C) 0
D) -2
Answer: A) +4
Explanation: In dinitrogen tetroxide (N2O4N2O4), the average oxidation state of nitrogen is +4.
Question 76:
In the electrochemical series, which of the following is a strong oxidizing agent?
A) LiLi
B) Ag+Ag+
C) F2F2
D) NaNa
Answer: C) F2F2
Explanation: Fluorine (F2F2) is a very strong oxidizing agent due to its high electronegativity.
Question 77:
What is the role of Cl−Cl− in the reaction Cl2+2e−→2Cl−Cl2+2e−→2Cl−?
A) Oxidizing agent
B) Reducing agent
C) Both oxidizing and reducing agent
D) None of the above
Answer: A) Oxidizing agent
Explanation: Cl−Cl− is formed by the reduction of Cl2Cl2, making it an oxidizing agent.
Question 78:
In the reaction H2+F2→2HFH2+F2→2HF, which species is reduced?
A) H2H2
B) F2F2
C) HFHF
D) None of the above
Answer: B) F2F2
Explanation: Fluorine is reduced as it gains electrons going from 0 in F2F2 to -1 in HFHF.
Question 79:
Which of the following best describes a reducing agent?
A) A species that gains electrons.
B) A species that loses electrons.
C) A species that does not change oxidation state.
D) None of the above.
Answer: B) A species that loses electrons.
Explanation: A reducing agent donates electrons and is oxidized in the process.
Question 80:
What is the oxidation state of iodine in ICl3ICl3?
A) +1
B) +3
C) +5
D) +7
Answer: B) +3
Explanation: In iodine trichloride (ICl3ICl3), iodine has an oxidation state of +3.
Question 81:
Which of the following represents a loss of electrons?
A) Reduction
B) Oxidation
C) Neutralization
D) Hydrolysis
Answer: B) Oxidation
Explanation: Oxidation is defined as the loss of electrons.
Question 82:
What is the oxidation state of carbon in carbon dioxide (CO2CO2)?
A) +4
B) +2
C) 0
D) -2
Answer: A) +4
Explanation: In carbon dioxide, carbon has an oxidation state of +4.
Question 83:
Which of the following species is most likely to be reduced?
A) Na+Na+
B) Cl−Cl−
C) Cu2+Cu2+
D) Ca2+Ca2+
Answer: C) Cu2+Cu2+
Explanation: Copper ions can gain electrons to become elemental copper, making them likely to be reduced.
Question 84:
Which of the following processes involves oxidation?
A) Fe2+→Fe3++e−Fe2+→Fe3++e−
B) Cu2++2e−→CuCu2++2e−→Cu
C) Ag+e−→Ag+Ag+e−→Ag+
D) O2+4e−→2O2−O2+4e−→2O2−
Answer: A) Fe2+→Fe3++e−Fe2+→Fe3++e−
Explanation: This reaction shows iron losing an electron, which is oxidation.
Question 85:
In the reaction 2MnO4−+5C2O42−+6H+→2Mn2++10CO2+3H2O2MnO4−+5C2O42−+6H+→2Mn2++10CO2+3H2O, what happens to manganese?
A) It is oxidized.
B) It is reduced.
C) It remains unchanged.
D) None of the above.
Answer: B) It is reduced.
Explanation: Manganese is reduced from +7 in MnO4−MnO4− to +2 in Mn2+Mn2+.
Question 86:
Which of the following substances can act as both an oxidizing and a reducing agent?
A) H2OH2O
B) H2O2H2O2
C) NaClNaCl
D) NH3NH3
Answer: B) H2O2H2O2
Explanation: Hydrogen peroxide can both gain and lose electrons, making it versatile in redox reactions.
Question 87:
What is the oxidation state of iron in Fe2O3Fe2O3?
A) +2
B) +3
C) 0
D) -3
Answer: B) +3
Explanation: In iron(III) oxide (Fe2O3Fe2O3), iron has an oxidation state of +3.
Question 88:
Which of the following is a common application of redox reactions?
A) Battery operation
B) Combustion processes
C) Corrosion
D) All of the above
Answer: D) All of the above
Explanation: Redox reactions play critical roles in batteries, combustion, and corrosion processes.
Question 89:
What is the oxidation state of chlorine in ClO2−ClO2−?
A) +1
B) +3
C) +4
D) -1
Answer: B) +3
Explanation: In the chlorite ion (ClO2−ClO2−), chlorine has an oxidation state of +3.
Question 90:
In the reaction 4Fe+3O2→2Fe2O34Fe+3O2→2Fe2O3, what is happening to iron?
A) It is oxidized.
B) It is reduced.
C) It remains unchanged.
D) It is neutralized.
Answer: A) It is oxidized.
Explanation: Iron loses electrons to form Fe2O3Fe2O3, indicating oxidation.
Question 91:
What is the oxidation state of manganese in MnO4−MnO4−?
A) +4
B) +6
C) +7
D) -2
Answer: C) +7
Explanation: In the permanganate ion, manganese has an oxidation state of +7.
Question 92:
Which of the following species is a strong oxidizing agent?
A) Cr2O72−Cr2O72−
B) H2O2H2O2
C) I−I−
D) LiLi
Answer: A) Cr2O72−Cr2O72−
Explanation: The dichromate ion is a powerful oxidizing agent in acidic conditions.
Question 93:
Which of the following statements is true about oxidation and reduction?
A) Oxidation is always accompanied by reduction.
B) Oxidation and reduction can occur independently.
C) Both processes involve the same species.
D) Only oxidation involves the transfer of electrons.
Answer: A) Oxidation is always accompanied by reduction.
Explanation: Oxidation and reduction are coupled processes that occur together in a redox reaction.
Question 94:
What is the oxidation state of carbon in acetic acid (CH3COOHCH3COOH)?
A) +1
B) +2
C) +3
D) +4
Answer: C) +3
Explanation: The oxidation state of the carbon atom in acetic acid is +3.
Question 95:
Which of the following best describes the term “oxidizing agent”?
A) A substance that gains electrons.
B) A substance that loses electrons.
C) A substance that remains unchanged.
D) A substance that only undergoes reduction.
Answer: A) A substance that gains electrons.
Explanation: An oxidizing agent accepts electrons and is reduced in a redox reaction.
Question 96:
In which of the following reactions is nitrogen oxidized?
A) NH3→N2+H2NH3→N2+H2
B) N2+3H2→2NH3N2+3H2→2NH3
C) NO+O2→NO2NO+O2→NO2
D) N2O+H2→N2+H2ON2O+H2→N2+H2O
Answer: C) NO+O2→NO2NO+O2→NO2
Explanation: Nitrogen in nitric oxide is oxidized from +2 to +4 in NO2NO2.
Question 97:
What is the oxidation state of sulfur in H2SO4H2SO4?
A) +2
B) +4
C) +6
D) 0
Answer: C) +6
Explanation: In sulfuric acid (H2SO4H2SO4), sulfur has an oxidation state of +6.
Question 98:
Which of the following ions is a common oxidizing agent?
A) Fe2+Fe2+
B) Cu+Cu+
C) Cr2O72−Cr2O72−
D) AgAg
Answer: C) Cr2O72−Cr2O72−
Explanation: The dichromate ion is frequently used as an oxidizing agent in redox reactions.
Question 99:
What happens to the oxidation state of chlorine in the reaction Cl2+2NaOH→NaCl+NaClO+H2OCl2+2NaOH→NaCl+NaClO+H2O?
A) It is reduced.
B) It is oxidized.
C) It remains unchanged.
D) It becomes negative.
Answer: B) It is oxidized.
Explanation: Chlorine in NaClONaClO has a higher oxidation state than in NaClNaCl, indicating oxidation.
Question 100:
In which of the following pairs of species does one undergo oxidation and the other reduction?
A) ZnZn and Cu2+Cu2+
B) AgAg and NaNa
C) Cl−Cl− and O2O2
D) Fe2+Fe2+ and H2H2
Answer: A) ZnZn and Cu2+Cu2+
Explanation: In this reaction, zinc is oxidized while copper is reduced, demonstrating a redox process.
Question 101:
What is the oxidation state of nitrogen in NO2NO2?
A) +2
B) +4
C) 0
D) -2
Answer: B) +4
Explanation: In nitrogen dioxide (NO2NO2), nitrogen has an oxidation state of +4.
Question 102:
Which of the following is a product of the oxidation of glucose in cellular respiration?
A) Oxygen
B) Carbon dioxide
C) Water
D) Both B and C
Answer: D) Both B and C
Explanation: The oxidation of glucose results in the production of carbon dioxide and water.
Question 103:
In the reaction 2FeCl3+Sn→2FeCl2+SnCl22FeCl3+Sn→2FeCl2+SnCl2, which species is the reducing agent?
A) FeCl3FeCl3
B) FeCl2FeCl2
C) SnSn
D) SnCl2SnCl2
Answer: C) SnSn
Explanation: Tin (Sn) is oxidized and donates electrons, acting as the reducing agent.
Question 104:
Which of the following statements is true about a reduction reaction?
A) It involves the loss of electrons.
B) It involves the gain of protons.
C) It involves the gain of electrons.
D) It results in an increase in oxidation state.
Answer: C) It involves the gain of electrons.
Explanation: Reduction is characterized by the gain of electrons.
Question 105:
What is the oxidation state of sulfur in SO2SO2?
A) +2
B) +4
C) 0
D) -2
Answer: B) +4
Explanation: In sulfur dioxide (SO2SO2), sulfur has an oxidation state of +4.
Question 106:
In a redox reaction, which statement is always true?
A) The same species is oxidized and reduced.
B) The total number of electrons lost equals the total number of electrons gained.
C) Only one species is involved.
D) All reactions are spontaneous.
Answer: B) The total number of electrons lost equals the total number of electrons gained.
Explanation: In a redox reaction, electron conservation is maintained.
Question 107:
What is the oxidation state of chromium in CrO3CrO3?
A) +3
B) +6
C) +5
D) 0
Answer: B) +6
Explanation: In chromium trioxide (CrO3CrO3), chromium has an oxidation state of +6.
Question 108:
In the reaction Zn+2HCl→ZnCl2+H2Zn+2HCl→ZnCl2+H2, what happens to zinc?
A) It is oxidized.
B) It is reduced.
C) It remains unchanged.
D) It is neutralized.
Answer: A) It is oxidized.
Explanation: Zinc is oxidized as it loses electrons to form Zn2+Zn2+.
Question 109:
Which of the following compounds is formed during the oxidation of SO2SO2?
A) SO3SO3
B) S8S8
C) H2SO4H2SO4
D) Both A and C
Answer: D) Both A and C
Explanation: Sulfur dioxide can be oxidized to form both sulfur trioxide and sulfuric acid.
Question 110:
What is the oxidation state of lead in PbO2PbO2?
A) +2
B) +4
C) 0
D) -2
Answer: B) +4
Explanation: In lead(IV) oxide (PbO2PbO2), lead has an oxidation state of +4.
Question 111:
Which ion is commonly used as a reducing agent in organic reactions?
A) Li+Li+
B) Na+Na+
C) H2H2
D) Cl−Cl−
Answer: C) H2H2
Explanation: Hydrogen gas can act as a reducing agent in many organic reactions.
Question 112:
What is the oxidation state of iron in Fe3O4Fe3O4?
A) +2
B) +3
C) +4
D) +6
Answer: B) +3
Explanation: In magnetite (Fe3O4Fe3O4), the average oxidation state of iron is +3.
Question 113:
In the reaction 2H2O2→2H2O+O22H2O2→2H2O+O2, what happens to the oxidation state of oxygen?
A) It increases.
B) It decreases.
C) It remains the same.
D) It changes to zero.
Answer: A) It increases.
Explanation: In this reaction, oxygen in H2O2H2O2 is oxidized from -1 to 0 in O2O2.
Question 114:
What is the oxidation state of the central atom in H3PO4H3PO4?
A) +1
B) +3
C) +5
D) 0
Answer: C) +5
Explanation: In phosphoric acid (H3PO4H3PO4), phosphorus has an oxidation state of +5.
Question 115:
Which of the following reactions does not involve a change in oxidation states?
A) Zn+2Ag+→2Ag+Zn2+Zn+2Ag+→2Ag+Zn2+
B) 2H2+O2→2H2O2H2+O2→2H2O
C) C+O2→CO2C+O2→CO2
D) CaCO3→CaO+CO2CaCO3→CaO+CO2
Answer: D) CaCO3→CaO+CO2CaCO3→CaO+CO2
Explanation: This reaction involves no change in oxidation states of calcium or carbon.
Question 116:
In the reaction 4HCl+MnO4−+2H2O→Cl2+MnCl2+4H2O4HCl+MnO4−+2H2O→Cl2+MnCl2+4H2O, what happens to manganese?
A) It is oxidized.
B) It is reduced.
C) It remains unchanged.
D) It is neutralized.
Answer: B) It is reduced.
Explanation: Manganese is reduced from +7 in MnO4−MnO4− to +2 in MnCl2MnCl2.
Question 117:
What is the oxidation state of phosphorus in P4O10P4O10?
A) +5
B) +3
C) +4
D) 0
Answer: A) +5
Explanation: In tetraphosphorus decoxide (P4O10P4O10), phosphorus has an oxidation state of +5.
Question 118:
In a redox reaction, which component is responsible for providing electrons?
A) Reducing agent
B) Oxidizing agent
C) Both agents
D) Neither
Answer: A) Reducing agent
Explanation: The reducing agent donates electrons and is oxidized in the process.
Question 119:
What is the oxidation state of chlorine in sodium hypochlorite (NaClONaClO)?
A) +1
B) +3
C) +5
D) -1
Answer: A) +1
Explanation: In sodium hypochlorite, chlorine has an oxidation state of +1.
Question 120:
Which of the following metals cannot be oxidized by Cu2+Cu2+?
A) ZnZn
B) AgAg
C) AuAu
D) FeFe
Answer: C) AuAu
Explanation: Gold is less reactive and cannot be oxidized by Cu2+Cu2+.
Question 121:
What is the oxidation state of carbon in acetylene (C2H2C2H2)?
A) 0
B) +1
C) -1
D) +2
Answer: C) -1
Explanation: Each carbon atom in acetylene has an oxidation state of -1.
Question 122:
Which ion is commonly produced in the oxidation of sulfur in the environment?
A) SO32−SO32−
B) SO42−SO42−
C) H2SH2S
D) HS−HS−
Answer: B) SO42−SO42−
Explanation: Sulfur is often oxidized to sulfate ions in environmental processes.
Question 123:
What happens to the oxidation state of magnesium when it reacts with oxygen to form magnesium oxide (MgOMgO)?
A) It decreases.
B) It increases.
C) It remains the same.
D) It is neutralized.
Answer: B) It increases.
Explanation: Magnesium is oxidized from 0 to +2 in magnesium oxide.
Question 124:
Which of the following compounds can act as a reducing agent?
A) H2OH2O
B) O2O2
C) NaNa
D) Cl2Cl2
Answer: C) NaNa
Explanation: Sodium can lose electrons and act as a reducing agent.
Question 125:
What is the oxidation state of phosphorus in H3PO3H3PO3?
A) +3
B) +5
C) +2
D) 0
Answer: A) +3
Explanation: In phosphorous acid (H3PO3H3PO3), phosphorus has an oxidation state of +3.
Question 126:
In the reaction Cu2++2e−→CuCu2++2e−→Cu, what is happening to copper?
A) It is oxidized.
B) It is reduced.
C) It remains unchanged.
D) It is neutralized.
Answer: B) It is reduced.
Explanation: Copper ions gain electrons to form elemental copper, indicating reduction.
Question 127:
Which of the following statements about redox reactions is true?
A) Oxidation and reduction can occur independently of each other.
B) Electrons are always lost during reduction.
C) Oxidation always occurs with reduction.
D) Redox reactions do not involve any electron transfer.
Answer: C) Oxidation always occurs with reduction.
Explanation: In redox reactions, oxidation and reduction are coupled processes.
Question 128:
What is the oxidation state of sulfur in H2SH2S?
A) +2
B) +4
C) -2
D) 0
Answer: C) -2
Explanation: In hydrogen sulfide, sulfur has an oxidation state of -2.
Question 129:
In the reaction C6H14+O2→CO2+H2OC6H14+O2→CO2+H2O, what is being oxidized?
A) Oxygen
B) Carbon
C) Hydrogen
D) None of the above
Answer: B) Carbon
Explanation: Carbon in hydrocarbons is oxidized to form carbon dioxide.
Question 130:
Which of the following species is a strong reducing agent?
A) H2H2
B) Cl−Cl−
C) F−F−
D) O2O2
Answer: A) H2H2
Explanation: Hydrogen gas can donate electrons, acting as a strong reducing agent.
Question 131:
What is the oxidation state of oxygen in H2O2H2O2?
A) -1
B) 0
C) -2
D) +2
Answer: A) -1
Explanation: In hydrogen peroxide, oxygen has an oxidation state of -1.
Question 132:
In which of the following pairs does one species undergo oxidation while the other undergoes reduction?
A) Fe+Ag+→Fe2++AgFe+Ag+→Fe2++Ag
B) Na+Cl2→NaClNa+Cl2→NaCl
C) Cu2++Zn→Cu+Zn2+Cu2++Zn→Cu+Zn2+
D) All of the above
Answer: D) All of the above
Explanation: Each reaction involves one species being oxidized and another being reduced.
Question 133:
Which of the following compounds is a strong oxidizing agent?
A) Fe3+Fe3+
B) I−I−
C) AgAg
D) KMnO4KMnO4
Answer: D) KMnO4KMnO4
Explanation: Potassium permanganate is commonly used as a strong oxidizing agent in redox reactions.
Question 134:
What is the oxidation state of zinc in ZnCl2ZnCl2?
A) +1
B) +2
C) 0
D) -1
Answer: B) +2
Explanation: In zinc chloride, zinc has an oxidation state of +2.
Question 135:
In the reaction 2Ag++Zn→2Ag+Zn2+2Ag++Zn→2Ag+Zn2+, which species is oxidized?
A) Ag+Ag+
B) ZnZn
C) Zn2+Zn2+
D) None of the above
Answer: B) ZnZn
Explanation: Zinc loses electrons and is oxidized to Zn2+Zn2+.
Question 136:
What is the oxidation state of nitrogen in N2H4N2H4?
A) -2
B) 0
C) +1
D) +2
Answer: C) +1
Explanation: In hydrazine (N2H4N2H4), the oxidation state of nitrogen is +1.
Question 137:
Which of the following statements is true for the reaction 2Ag+Cu2+→2Ag++Cu2Ag+Cu2+→2Ag++Cu?
A) Silver is oxidized and copper is reduced.
B) Copper is oxidized and silver is reduced.
C) Both silver and copper are oxidized.
D) Both silver and copper are reduced.
Answer: A) Silver is oxidized and copper is reduced.
Explanation: Silver loses electrons, while copper gains electrons.
Question 138:
What is the oxidation state of the central atom in CrCl3CrCl3?
A) +3
B) +5
C) +6
D) 0
Answer: A) +3
Explanation: In chromium(III) chloride, chromium has an oxidation state of +3.
Question 139:
Which of the following is a product of the reduction of Fe3+Fe3+?
A) FeFe
B) Fe2+Fe2+
C) Fe2O3Fe2O3
D) FeOFeO
Answer: B) Fe2+Fe2+
Explanation: The reduction of Fe3+Fe3+ results in Fe2+Fe2+.
Question 140:
What is the oxidation state of aluminum in Al2O3Al2O3?
A) +1
B) +2
C) +3
D) 0
Answer: C) +3
Explanation: In aluminum oxide, aluminum has an oxidation state of +3.
Question 141:
Which of the following compounds can be oxidized by Ag+Ag+?
A) H2H2
B) CH3OHCH3OH
C) CuCu
D) NaNa
Answer: B) CH3OHCH3OH
Explanation: Methanol can be oxidized to formaldehyde or further, and silver ions can participate in this reaction.
Question 142:
What is the oxidation state of manganese in KMnO4KMnO4?
A) +4
B) +6
C) +7
D) +2
Answer: C) +7
Explanation: In potassium permanganate, manganese has an oxidation state of +7.
Question 143:
In the reaction Ca+Cl2→CaCl2Ca+Cl2→CaCl2, what is the oxidation state of calcium after the reaction?
A) 0
B) +2
C) -2
D) +1
Answer: B) +2
Explanation: Calcium is oxidized from 0 to +2 in calcium chloride.
Question 144:
What is the oxidation state of chromium in Cr2O72−Cr2O72−?
A) +3
B) +6
C) +4
D) +7
Answer: B) +6
Explanation: In the dichromate ion, chromium has an oxidation state of +6.
Question 145:
Which of the following elements can act as an oxidizing agent?
A) I−I−
B) O2O2
C) H−H−
D) LiLi
Answer: B) O2O2
Explanation: Molecular oxygen can accept electrons, making it an oxidizing agent.
Question 146:
What is the oxidation state of iodine in KIKI?
A) -1
B) +1
C) +2
D) +3
Answer: A) -1
Explanation: In potassium iodide, iodine has an oxidation state of -1.
Question 147:
In the reaction 2H2+O2→2H2O2H2+O2→2H2O, what happens to the oxidation state of hydrogen?
A) It decreases.
B) It increases.
C) It remains the same.
D) It becomes zero.
Answer: C) It remains the same.
Explanation: The oxidation state of hydrogen remains +1 throughout the reaction.
Question 148:
What is the oxidation state of tin in SnCl2SnCl2?
A) +2
B) +4
C) 0
D) -2
Answer: A) +2
Explanation: In tin(II) chloride, tin has an oxidation state of +2.
Question 149:
Which of the following represents a reduction reaction?
A) Zn→Zn2++2e−Zn→Zn2++2e−
B) Cu2++2e−→CuCu2++2e−→Cu
C) Na→Na++e−Na→Na++e−
D) None of the above
Answer: B) Cu2++2e−→CuCu2++2e−→Cu
Explanation: This reaction shows copper ions gaining electrons, indicating reduction.
Question 150:
In which of the following pairs of elements does one undergo oxidation and the other undergo reduction?
A) LiLi and ClCl
B) CC and H2H2
C) FeFe and SS
D) All of the above
Answer: D) All of the above
Explanation: Each pair shows one element being oxidized and another being reduced.
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