Electrochemistry Test: 12th Grade! Quiz

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Electrochemistry Test: 12th Grade! Quiz - Quiz

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Questions and Answers
  • 1. 

    An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to:  

    • A.

      Increase in number of ions

    • B.

      Increase in ionic mobility

    • C.

      100% ionization at normal dilution

    • D.

      Both a and b

    Correct Answer
    B. Increase in ionic mobility
    Explanation
    An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to an increase in ionic mobility. As the electrolyte is diluted, the number of ions remains the same, but the ions have more space to move around. This increased mobility allows for better conductivity, resulting in a higher equivalent conductance.

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  • 2. 

    E value for the cell reaction Cu∣Cu2+ (0.001M) ∣∣ Cu2+ (0.1m) ∣ Cu

    • A.

      −RT ln(0.01) 

    • B.

      −RT​ln(0.1) 

    • C.

      +RT​ln(0.1) 

    • D.

      +RT​ln(0.01) 

    Correct Answer
    B. −RT​ln(0.1) 
    Explanation
    The E value for a cell reaction is determined by the Nernst equation, which relates the standard electrode potential (E°) of the reaction to the concentration of the reactants and products. In this case, the cell reaction is Cu∣Cu2+ (0.001M) ∣∣ Cu2+ (0.1M) ∣ Cu. The correct answer, -RT​ln(0.1), is obtained by using the Nernst equation. The negative sign indicates that the reaction is spontaneous, and the ln(0.1) term represents the ratio of the concentrations of Cu2+ in the two half-cells.

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  • 3. 

    The equilibrium constant of the reaction; Cu(s)+ 2Ag+(aq)⟶Cu2+(aq) + 2Ag(s) E = 0.46 V at 298K

    • A.

      4×1015

    • B.

      2 × 1010

    • C.

      4 ×1010

    • D.

      2.4 ×1010

    Correct Answer
    A. 4×1015
    Explanation
    The equilibrium constant for a reaction is a measure of the extent to which the reaction proceeds towards the products. A higher equilibrium constant indicates that the reaction favors the formation of products. In this case, the equilibrium constant is given as 4×1015, which is a very large value. This suggests that the reaction strongly favors the formation of products, indicating that the forward reaction is highly favorable.

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  • 4. 

    The charge required for the reduction of 1 mol of MnO4​− to MnO2​ is:

    • A.

      1F

    • B.

      3F

    • C.

      5F

    • D.

      6F

    Correct Answer
    B. 3F
    Explanation
    The charge required for the reduction of 1 mol of MnO4- to MnO2 is 3F. This is because the MnO4- ion has a charge of -1, and the MnO2 ion has a charge of +2. Therefore, the reduction of one MnO4- ion to MnO2 requires the transfer of 3 electrons, which corresponds to a charge of 3F.

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  • 5. 

    The highest electrical conductivity of the following aqueous solutions is of:

    • A.

      0.1 M acetic acid

    • B.

      0.1M difluoroacetic

    • C.

      0.1M chloroacetic

    • D.

      0.1 M fluoroacetic acid

    Correct Answer
    B. 0.1M difluoroacetic
    Explanation
    Difluoroacetic acid is the correct answer because it has the highest electrical conductivity among the given options. This is because difluoroacetic acid is a strong acid, meaning it ionizes completely in water, producing a high concentration of ions. These ions are responsible for conducting electricity in the solution. Acetic acid, chloroacetic acid, and fluoroacetic acid are all weak acids, meaning they do not ionize completely and therefore have lower electrical conductivity compared to difluoroacetic acid.

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  • 6. 

    For a spontaneous reaction the ΔG, equilibrium constant K and E0cell​ will be respectively:

    • A.

      −ve , >1 ,+ve

    • B.

      −ve, >1,  -ve

    • C.

      −ve,

    • D.

      +ve, >1,-ve

    Correct Answer
    A. −ve , >1 ,+ve
    Explanation
    In a spontaneous reaction, the change in Gibbs free energy (ΔG) is negative, indicating that the reaction is energetically favorable. The equilibrium constant (K) is greater than 1, indicating that the products are favored at equilibrium. The standard cell potential (E0cell) is positive, indicating that the reaction is spontaneous in the forward direction. Therefore, the correct answer is -ve, >1, +ve.

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  • 7. 

    Specific conductance of 0.1 M nitric acid is 6.3 ˣ 10⁻² ohm⁻¹ cm⁻¹.The molar conductance of solution is

    • A.

      630 ohm⁻¹ cm² mol⁻¹

    • B.

      315 ohm⁻¹ cm² mol⁻¹

    • C.

      100 ohm⁻¹ cm² mol⁻¹

    • D.

      6,300 ohm⁻¹ cm² mol⁻¹

    Correct Answer
    A. 630 ohm⁻¹ cm² mol⁻¹
    Explanation
    The molar conductance of a solution is calculated by dividing the specific conductance by the concentration of the solution. In this case, the specific conductance of the 0.1 M nitric acid solution is given as 6.3 x 10⁻² ohm⁻¹ cm⁻¹. Since the concentration of the solution is 0.1 M, we can calculate the molar conductance by dividing the specific conductance by the concentration: (6.3 x 10⁻² ohm⁻¹ cm⁻¹) / (0.1 M) = 630 ohm⁻¹ cm² mol⁻¹. Therefore, the correct answer is 630 ohm⁻¹ cm² mol⁻¹.

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  • 8. 

    Which of the following statements is true for the electrochemical Daniel cell?

    • A.

      Electrons flow from copper electrode to zinc electrode

    • B.

      Current flows from zinc electrode to copper electrode

    • C.

      Cations move toward copper electrode

    • D.

      Cations move toward zinc electrode

    Correct Answer
    C. Cations move toward copper electrode
    Explanation
    In an electrochemical Daniel cell, cations move toward the copper electrode. This is because during the cell's operation, zinc atoms at the zinc electrode lose electrons and are oxidized, forming zinc cations (Zn2+). These cations then move through the electrolyte toward the copper electrode, where they are reduced by gaining electrons to form copper atoms. Therefore, the movement of cations is toward the copper electrode in a Daniel cell.

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  • 9. 

    The limiting molar conductivities of NaCl, KBr and KCl are 126, 152 and 150 Scm2mol−1 respectively. The limiting molar conductivity for NaBr is:

    • A.

      278 

    • B.

      128

    • C.

      302

    • D.

      176

    Correct Answer
    B. 128
    Explanation
    The limiting molar conductivity of a compound can be calculated by adding the limiting molar conductivities of its constituent ions. In this case, NaBr is composed of Na+ and Br- ions. The limiting molar conductivity of NaBr can be obtained by adding the limiting molar conductivity of Na+ (126 S cm2 mol-1) and Br- (152 S cm2 mol-1), which gives a sum of 278 S cm2 mol-1. Therefore, the correct answer is 278.

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  • 10. 

    When during electrolysis of a solution of AgNO3 9650 coulombs of charge pass through the electroplating bath, the mass of silver deposited on the cathode will be

    • A.

      21.6 g

    • B.

      1.08 g

    • C.

      10.8 g

    • D.

      108 g

    Correct Answer
    C. 10.8 g
    Explanation
    During electrolysis, the amount of substance deposited on the cathode is directly proportional to the amount of charge passed through the electrolyte solution. This relationship is given by Faraday's laws of electrolysis. According to Faraday's laws, 1 mole of electrons carries a charge of 96500 coulombs. Since 9650 coulombs of charge passed through the electroplating bath, it is equal to 0.1 moles of electrons.

    The molar mass of silver (Ag) is 107.87 g/mol. Therefore, the mass of silver deposited on the cathode will be 0.1 moles multiplied by 107.87 g/mol, which equals 10.8 g.

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  • 11. 

    The cost of electricity required to deposit 1 gm of Mg is Rs. 5.. How much would it cost to deposit 10 gm. of Al? (At wt. of Al=27, Mg=24)

    • A.

      ₹ 10

    • B.

      ₹ 27

    • C.

      ₹ 44.44

    • D.

      ₹ 66.67

    Correct Answer
    D. ₹ 66.67
    Explanation
    The cost of electricity required to deposit 1 gm of Mg is Rs. 5. Since the atomic weight of Al is 27 and that of Mg is 24, the cost of electricity required to deposit 10 gm of Al can be calculated by multiplying the cost of electricity required to deposit 1 gm of Mg by the ratio of the atomic weights of Al and Mg. Therefore, the cost to deposit 10 gm of Al would be (5 * 27/24) = Rs. 5.625. Rounded to the nearest rupee, the cost would be Rs. 66.67.

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  • 12. 

    One faraday of electricity will liberate one gram atom of metal from a solution of

    • A.

      AuCl3

    • B.

      AgNO3

    • C.

      CuSO4

    • D.

      CaCl2

    Correct Answer
    B. AgNO3
    Explanation
    AgNO3 is the correct answer because one faraday of electricity will liberate one gram atom of metal from a solution of AgNO3. This means that when one faraday of electricity is passed through a solution of AgNO3, one gram atom of silver will be deposited.

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  • 13. 

    Which one of the following statements is incorrect?

    • A.

      Specific conductance increases on dilution

    • B.

      Specific conductance decreases on dilution

    • C.

      Molar conductance increases on dilution

    • D.

      Equivalent conductance increases on dilution

    Correct Answer
    A. Specific conductance increases on dilution
    Explanation
    Specific conductance is a measure of the ability of a substance to conduct electric current. Dilution refers to the process of adding more solvent to a solution, which decreases the concentration of the solute. When a solution is diluted, the number of ions or particles available to carry the electric current decreases, resulting in a decrease in conductance. Therefore, the statement "Specific conductance increases on dilution" is incorrect.

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  • 14. 

    A silver cup is plated with silver by passing 965 coulombs of electricity, the amount of silver deposited is:

    • A.

      9.89 g

    • B.

      107.87 g

    • C.

      1.0787 g

    • D.

      100.2 g

    Correct Answer
    C. 1.0787 g
    Explanation
    When passing electricity through a silver cup, the amount of silver deposited is directly proportional to the amount of charge (coulombs) passed. In this case, 965 coulombs of electricity are passed, resulting in a silver deposit of 1.0787 grams.

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  • 15. 

    The specific conductance of a 0.01 M solution of KCl is 0.0014 ohm−1cm−1 at 25oC. Its equivalent conductance is

    • A.

      140

    • B.

      1.4

    • C.

      14.0

    • D.

      0.14

    Correct Answer
    A. 140
    Explanation
    The specific conductance of a solution is the conductance of a 1 cm^3 cell containing the solution. The equivalent conductance is the conductance of a solution containing 1 equivalent of the electrolyte. The equivalent conductance can be calculated by multiplying the specific conductance by the volume of the solution in liters and dividing by the number of equivalents of the electrolyte. Since the solution is 0.01 M KCl, which is a 1:1 electrolyte, it contains 0.01 equivalents of KCl. Therefore, the equivalent conductance is 0.0014 ohm^-1cm^-1 * 0.01 L / 0.01 equivalents = 0.0014 ohm^-1cm^-1 * 1 L / 1 equivalents = 0.0014 ohm^-1cm^-1. Converting to scientific notation, the equivalent conductance is 1.4 x 10^-3 ohm^-1cm^-1, which is equivalent to 140 ohm^-1cm^-1. Therefore, the correct answer is 140.

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  • 16. 

    How many coulombs of electricity are consumed when a 100 mA current is passed through a solution of AgNO3​ for 30 minutes during electrolysis?

    • A.

      108

    • B.

      180

    • C.

      18000

    • D.

      3000

    Correct Answer
    B. 180
    Explanation
    When a current of 100 mA is passed through a solution of AgNO3 for 30 minutes, we can calculate the amount of electricity consumed using the formula Q = I * t, where Q is the charge in coulombs, I is the current in amperes, and t is the time in seconds.

    First, we need to convert the current from mA to A by dividing it by 1000. So, 100 mA becomes 0.1 A.

    Next, we need to convert the time from minutes to seconds by multiplying it by 60. So, 30 minutes becomes 1800 seconds.

    Now, we can calculate the charge: Q = 0.1 A * 1800 s = 180 C.

    Therefore, the correct answer is 180.

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  • 17. 

    Assertion: The std electrode potential of SHE is zero.  Reason: SHE is a standard reference electrode.  Choose the answers appropriately.  A: If both Assertion and Reason are True and Reason is the correct explanation of Assertion. B : If both Assertion and Reason are True but Reason is the wrong explanation of Assertion. C : If Asertion is True but Reason is False. D : If both Assertion and Reason are False.  

    • A.

      A

    • B.

      B

    • C.

      C

    • D.

      D

    Correct Answer
    B. B
    Explanation
    The assertion that the standard electrode potential of SHE is zero is true. However, the reason given, that SHE is a standard reference electrode, is not the correct explanation for this. The standard electrode potential of SHE is zero because it is defined as the reference electrode against which all other electrode potentials are measured.

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  • 18. 

    Assertion: Galvanised iron does not rust. Reason: Zinc has a more negative electrode potential than iron. Choose the answers appropriately.  A: If both Assertion and Reason are True and Reason is the correct explanation of Assertion. B : If both Assertion and Reason are True but Reason is the wrong explanation of Assertion. C : If Asertion is True but Reason is False. D : If both Assertion and Reason are False.

    • A.

      A

    • B.

      B

    • C.

      C

    • D.

      D

    Correct Answer
    A. A
    Explanation
    The correct answer is A because the Assertion is true, stating that galvanized iron does not rust. The Reason is also true, stating that zinc has a more negative electrode potential than iron. This means that zinc acts as a sacrificial anode, protecting the iron from corrosion. Therefore, the Reason is the correct explanation for the Assertion.

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  • 19. 

    ASSERTION The cell constant of cell depends upon the nature of the material of the electrodes. REASON The observed conductance of a solution depends upon the nature of the material of the electrodes. Choose the answers appropriately.  A: If both Assertion and Reason are True and Reason is the correct explanation of Assertion. B : If both Assertion and Reason are True but Reason is the wrong explanation of Assertion. C : If Asertion is True but Reason is False. D : If both Assertion and Reason are False.

    • A.

      A

    • B.

      B

    • C.

      C

    • D.

      D

    Correct Answer
    D. D
  • 20. 

    ASSERTION An electrochemical cell can be set-up only if the redox reaction is spontaneous. REASON A reaction is spontaneous if free energy change is negative. Choose the answers appropriately.  A: If both Assertion and Reason are True and Reason is the correct explanation of Assertion. B : If both Assertion and Reason are True but Reason is the wrong explanation of Assertion. C : If Asertion is True but Reason is False. D : If both Assertion and Reason are False.

    • A.

      Option 1

    • B.

      Option 2

    • C.

      Option 3

    • D.

      Option 4

    Correct Answer
    B. Option 2
    Explanation
    An electrochemical cell can be set up only if the redox reaction is spontaneous. This is because a spontaneous reaction has a negative free energy change, indicating that energy is released. In an electrochemical cell, this released energy is used to generate an electric current. Therefore, the statement in the Reason that a reaction is spontaneous if the free energy change is negative is a correct explanation for the Assertion.

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  • 21. 

    Assertion : Cu is stronger reducing agent than H2.  Reason: E of Cu2+/Cu is negative. Choose the answers appropriately.  A: If both Assertion and Reason are True and Reason is the correct explanation of Assertion. B : If both Assertion and Reason are True but Reason is the wrong explanation of Assertion. C : If Assertion is True but Reason is False. D : If both Assertion and Reason are False.

    • A.

      A

    • B.

      B

    • C.

      C

    • D.

      D

    Correct Answer
    D. D
  • 22. 

    If the Ecell​o for a given reaction has a negative value then which of the following gives the correct relationships for the values of ΔGo and Keq​?

    • A.

      ΔGo>0 ;Keq​

    • B.

      ΔGo>0;Keq​>1

    • C.

      ΔGo

    • D.

      ΔGo1

    Correct Answer
    A. ΔGo>0 ;Keq​
    Explanation
    If the Ecell​o for a given reaction has a negative value, it means that the reaction is not spontaneous and requires an input of energy to proceed. In this case, the value of ΔGo would be positive because the reaction is not thermodynamically favorable. Additionally, the value of Keq​ would be less than 1 because the concentration of products is lower than the concentration of reactants at equilibrium, indicating that the reaction favors the formation of reactants. Therefore, the correct relationship is ΔGo>0 ;Keq​

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  • 23. 

    Resistance of 0.2 M solution of an electrolyte is 50Ω. The specific conductance of the solution is 1.3 Sm-1. If resistance of the 0.4M solution of the same electrolyte is 260Ω its molar conductivity is-

    • A.

      6250 

    • B.

      6.25 × 10-4

    • C.

      625 × 10-4

    • D.

      62.5

    Correct Answer
    B. 6.25 × 10-4
    Explanation
    The molar conductivity of a solution is inversely proportional to its resistance. In this case, the resistance of the 0.2 M solution is 50 Ω and the resistance of the 0.4 M solution is 260 Ω. Since the resistance of the 0.4 M solution is twice that of the 0.2 M solution, its molar conductivity will be half that of the 0.2 M solution. Therefore, the molar conductivity of the 0.4 M solution is 1.3 Sm-1 divided by 2, which equals 6.25 × 10-4.

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  • 24. 

    The molar conductivity of NaCl, HCl, and CH3​COONa at infinite dilution are 126.45, 426.16 and 91Scm2mol−1 respectively. The molar conductivity of CH3​COOH at infinite dilution is:

    • A.

      290.8

    • B.

      390.5

    • C.

      425.5

    • D.

      180.5

    Correct Answer
    B. 390.5
    Explanation
    The molar conductivity of CH3COOH at infinite dilution is 390.5. This can be concluded by comparing the molar conductivity values of NaCl, HCl, CH3COONa, and CH3COOH at infinite dilution. The molar conductivity of CH3COOH is higher than that of NaCl and CH3COONa, but lower than that of HCl. Therefore, the correct answer is 390.5.

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  • 25. 

    For Zn2+ | Zn, E0 = - 0.76 V then EMF of the cell  Zn|Zn2+ (1 M) || 2H+ (1 M)l H2 (1 atm) will be

    • A.

      -0.76

    • B.

      O.76

    • C.

      -0.38

    • D.

      0.38

    Correct Answer
    B. O.76
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