Tamil Nadu Board of Secondary EducationHSC Science Class 12th

# Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Chemistry Volume 1 and 2 Answers Guide chapter 9 - Electro Chemistry [Latest edition]

## Chapter 9: Electro Chemistry

Evaluation
Evaluation [Pages 62 - 67]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Chemistry Volume 1 and 2 Answers Guide Chapter 9 Electro Chemistry Evaluation [Pages 62 - 67]

Evaluation | Q 1. | Page 62

The number of electrons that have a total charge of 9650 coulombs is ____________.

• 6.22 × 1023

• 6.022 × 1024

• 6.022 × 1022

• 6.022 × 10−34

Evaluation | Q 2. | Page 62

Consider the following half cell reactions:

$\ce{Mn^{2+} + 2e^- -> Mn}$ E0 = –1.18 V

$\ce{Mn^{2+} -> Mn^{2+} + e^-}$ E0 = –1.51 V

The E0 for the reaction $\ce{3Mn^{2+} -> Mn + 2Mn^{3+}}$, and the possibility of the forward reaction are respectively.

• 2.69 V and spontaneous

• –2.69 V and non spontaneous

• 0.33 V and Spontaneous

• 4.18 V and non spontaneous

Evaluation | Q 3. | Page 62

The button cell used in watches functions as follows.

$\ce{Zn_{(s)} + Ag2O_{(s)} + H2O_{(l)} ⇌ 2Ag_{(s)} + Zn^{2+}_{( aq)} + 2OH^-_{( aq)}}$ the half cell potentials are $\ce{Ag2O_{(s)} + H2O_{(l)} + 2e^- -> 2Ag_{(s)} + 2OH^-_{( aq)}}$ E0 = 0.34 V The cell potential will be

• 0.84 V

• 1.34 V

• 1.10 V

• 0.42 V

Evaluation | Q 4. | Page 63

The molar conductivity of a 0.5 mol dm−3 solution of AgNO3 with electrolytic conductivity of 5.76 × 10−3 S cm−1 at 298 K is ____________.

• 2.88 S cm2 mol−1

• 11.52 S cm2 mol−1

• 0.086 S cm2 mol−1

• 28.8 S cm2 mol−1

Evaluation | Q 5. | Page 63
 Electrolyte KCl KNO3 HCl NaOAC NaCl Λ_(S cm mol−1) 149.9 145.0 426.2 91.0 126.5

Calculate $\ce{Λ^∘_{HOAC}}$ using appropriate molar conductances of the electrolytes listed above at infinite dilution in water at 25°C.

• 517.2

• 552.7

• 390.7

• 217.5

Evaluation | Q 6. | Page 63

Faradays constant is defined as ____________.

• charge carried by 1 electron

• charge carried by one mole of electrons

• charge required to deposit one mole of substance

• charge carried by 6.22 × 1010 electrons

Evaluation | Q 7. | Page 63

How many faradays of electricity are required for the following reaction to occur

$\ce{MnO^-_4 -> Mn^2+}$

• 5F

• 3F

• 1F

• 7F

Evaluation | Q 8. | Page 63

A current strength of 3.86 A was passed through molten Calcium oxide for 41minutes and 40 seconds. The mass of Calcium in grams deposited at the cathode is (atomic mass of Ca is 40g/mol and 1F = 96500 C).

• 4

• 2

• 8

• 6

Evaluation | Q 9. | Page 63

During electrolysis of molten sodium chloride, the time required to produce 0.1 mole of chlorine gas using a current of 3A is ___________.

• 55 minutes

• 107.2 minutes

• 220 minutes

• 330 minutes

Evaluation | Q 10. | Page 63

The number of electrons delivered at the cathode during electrolysis by a current of 1A in 60 seconds is ____________.
(charge of electron = 1.6 × 10−19 C)

• 6.22 × 1023

• 6.022 × 1020

• 3.75 × 1020

• 7.48 × 1023

Evaluation | Q 11. | Page 63

Which of the following electrolytic solution has the least specific conductance?

• 2N

• 0.002N

• 0.02N

• 0.2N

Evaluation | Q 12. | Page 63

• PbSO4 on cathode is reduced to Pb

• PbSO4 on anode is oxidised to PbO2

• PbSO4 on anode is reduced to Pb

• PbSO4 on cathode is oxidised to Pb

Evaluation | Q 13. | Page 64

Among the following cells

I) Leclanche cell

IV) Mercury cell

Primary cells are:

• I and IV

• I and III

• III and IV

• II and III

Evaluation | Q 14. | Page 64

Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because ____________.

• Zinc is lighter than iron

• Zinc has lower melting point than iron

• Zinc has lower negative electrode potential than iron

• Zinc has higher negative electrode potential than iron

Evaluation | Q 15. | Page 64

Assertion: pure iron when heated in dry air is converted with a layer of rust.

Reason: Rust has the compositionFe3O4.

• if both assertion and reason are true and reason is the correct explanation of assertion.

• if both assertion and reason are true but reason is not the correct explanation of assertion.

• assertion is true but reason is false.

• both assertion and reason are false.

Evaluation | Q 16. | Page 64

In $\ce{H2 - O2}$ fuel cell the reaction occurs at cathode is:

• $\ce{O2_{(g)} + 2H2O_{(l)} + 4e^- -> 4OH^-_{( aq)}}$

• $\ce{H^+_{( aq)} + OH^-_{( aq)} -> H2O_{(l)}}$

• $\ce{2H2_{(g)} + O2_{(g)} -> 2H2O_{(g)}}$

• $\ce{H^+ + e^- -> 1/2H2}$

Evaluation | Q 17. | Page 64

The equivalent conductance of "M"/36 solution of a weak monobasic acid is 6 mho cm2 equivalent−1 and at infinite dilution is 400 mho cm2 equivalent−1. The dissociation constant of this acid is ____________.

• 1.25 × 10−6

• 6.25 × 10−6

• 1.25 × 10−4

• 6.25 × 10−5

Evaluation | Q 18. | Page 64

A conductivity cell has been calibrated with a 0.01 M, 1 : 1 electrolytic solution (specific conductance (κ = 1.25 × 10−3 S cm−1) in the cell and the measured resistance was 800 Ω at 25°C. The cell constant is, ____________.

• 10−1 cm−1

• 101 cm−1

• 1 cm−1

• 5.7 × 10−12

Evaluation | Q 19. | Page 65

Conductivity of a saturated solution of a sparingly soluble salt AB (1 : 1 electrolyte) at 298 K is 1.85 × 10−5 S m−1. Solubility product of the salt AB at 298 K (Λ_"m"^∘)_"AB" = 14 × 10−3 S m2 mol−1.

• 5.7 × 10−3

• 1.32 × 10−12

• 7.5 × 10−12

• 1.74 × 10−12

Evaluation | Q 20. | Page 65

In the electrochemical cell: Zn|ZnSO4 (0.01 M)||CuSO4 (1.0 M)|Cu, the emf of this Daniel cell is E1. When the concentration of ZnSO4 is changed to 1.0 M and that CuSO4 changed to 0.01 M, the emf changes to E2. From the above, which one is the relationship between E1 and E2?

• E1 < E2

• E1 > E2

• E2 ≥ E1

• E1 = E2

Evaluation | Q 21. | Page 65

Consider the change in the oxidation state of Bromine corresponding to different emf values as shown in the diagram below:

$\ce{BrO^-_4 ->[1.82 V] BrO^-_3 ->[1.5 V] HBrO ->[1.595 V] Br2 ->[1.0652 V] Br^-}$

Then the species undergoing disproportionation is

• Br2

• $\ce{BrO^-_4}$

• $\ce{BrO^-_3}$

• HBrO

Evaluation | Q 22. | Page 65

For the cell reaction

$\ce{2Fe^{3+}_{( aq)} + 2l^-_{( aq)} -> 2Fe^{2+}_{( aq)} + l2_{( aq)}}$

$\ce{E^0_{cell}}$ = at 298 K. The standard Gibbs energy (∆G°) of the cell reactions is:

• – 46.32 KJ mol−1

• – 23.16 KJ mol−1

• 46.32 KJ mol−1

• 23.16 KJ mol−1

Evaluation | Q 23. | Page 65

A certain current liberated 0.504 gm of hydrogen in 2 hours. How many grams of copper can be liberated by the same current flowing for the same time through copper sulphate solution.

• 31.75

• 15.8

• 7.5

• 63.5

Evaluation | Q 24. | Page 65

A gas X at 1 atm is bubbled through a solution containing a mixture of 1MY and 1MZ at 25°C. If the reduction potential of Z > Y > X, then ____________.

• Y will oxidize X and not Z

• Y will oxidize Z and not X

• Y will oxidize both X and Z

• Y will reduce both X and Z

Evaluation | Q 25. | Page 65

Cell equation: $\ce{A + 2B^- -> A^{2+} + 2B}$

$\ce{A^{2+} + 2e^- -> A}$ E0 = +0.34 V and log10 k = 15.6 at 300 K for cell reactions find E0 for $\ce{B^+ + e^- -> B}$

• 0.80

• 1.26

• – 0.54

• – 10.94

Evaluation | Q 1. | Page 65

Define anode

Evaluation | Q 1. | Page 65

Define cathode

Evaluation | Q 2. | Page 65

Why does the conductivity of a solution decrease on dilution of the solution?

Evaluation | Q 3. | Page 65

State Kohlrausch law. How is it useful to determine the molar conductivity of weak electrolytes at infinite dilution?

Evaluation | Q 4. | Page 66

Describe the electrolysis of molten NaCl using inert electrodes.

Evaluation | Q 5. | Page 66

Evaluation | Q 6. | Page 66

Describe the construction of Daniel cell. Write the cell reaction.

Evaluation | Q 7. | Page 66

Why is anode in galvanic cell considered to be negative and cathode positive electrode?

Evaluation | Q 8. | Page 66

The conductivity of a 0.01 M solution of a 1 : 1 weak electrolyte at 298 K is 1.5 × 10−4 S cm−1.

i) molar conductivity of the solution

ii) degree of dissociation and the dissociation constant of the weak electrolyte

Given that

$\ce{λ^∘_{cation}}$ = 248.2 S cm2 mol−1

$\ce{λ^∘_{anion}}$ = 51.8 S cm2 mol−1

Evaluation | Q 9. | Page 66

Which of 0.1 M HCl and 0.1 M KCl do you expect to have greater Λ_"m"^∘ and why?

Evaluation | Q 10. | Page 66

Arrange the following solutions in the decreasing order of specific conductance.

i) 0.01 M KCl

ii) 0.005 M KCl

iii) 0.1 M KCl

iv) 0.25 M KCl

v) 0.5 M KCl

Evaluation | Q 11. | Page 66

Why is AC current used instead of DC in measuring the electrolytic conductance?

Evaluation | Q 12. | Page 66

0.1 M NaCl solution is placed in two different cells having cell constant 0.5 and 0.25 cm−1 respectively. Which of the two will have a greater value of specific conductance.

Evaluation | Q 13. | Page 66

A current of 1.608A is passed through 250 mL of 0.5 M solution of copper sulphate for 50 minutes. Calculate the strength of Cu2+ after electrolysis assuming volume to be constant and the current efficiency is 100%.

Evaluation | Q 14. | Page 66

Can Fe3+ oxidises bromide to bromine under standard conditions?

Given: $\ce{E^0_{{Fe^{3+}|Fe^{2+}}}}$ = 0.771 V

$\ce{E^0_{{Br_{2}|Br^-}}}$ = −1.09 V

Evaluation | Q 15. | Page 66

Is it possible to store copper sulphate in an iron vessel for a long time?

Given: $\ce{E^0_{{Cu^{2+}|{Cu}}}}$ = 0.34 V and $\ce{E^0_{{Fe^{2+}|{Fe}}}}$ = −0.44 V

Evaluation | Q 16. | Page 66

Two metals M1 and M2 have reduction potential values of −xV and +yV respectively. Which will liberate H2 and H2SO4.

Evaluation | Q 17. | Page 66

Reduction potential of two metals M1 and M2 are $\ce{E^0_{{M_1^{2+}|M_1}}}$ = −2.3 V and $\ce{E^0_{{M_2^{2+}|M_2}}}$ = 0.2 V. Predict which one is better for coating the surface of iron.
Given: $\ce{E^0_{{Fe^{2+}|Fe}}}$ = −0.44 V

Evaluation | Q 18. | Page 66

Calculate the standard emf of the cell: $\ce{Cd|Cd^{2+}||Cu^{2+}|Cu}$ and determine the cell reaction. The standard reduction potentials of Cu2+|Cu and Cd2+|Cd are 0.34 V and −0.40 volts respectively. Predict the feasibility of the cell reaction.

Evaluation | Q 19. | Page 67

In fuel cell H2 and O2 react to produce electricity. In the process, H2 gas is oxidised at the anode and O2 at cathode. If 44.8 litre of H2 at 25°C and 1 atm pressure reacts in 10 minutes, what is average current produced? If the entire current is used for electro deposition of Cu from Cu2+, how many grams of deposited?

Evaluation | Q 20. | Page 67

The same amount of electricity was passed through two separate electrolytic cells containing solutions of nickel nitrate and chromium nitrate respectively. If 2.935 g of Ni was deposited in the first cell. The amount of Cr deposited in the another cell?
Given: molar mass of Nickel and chromium are 58.74 and 52 gm−1 respectively.

Evaluation | Q 21. | Page 67

A copper electrode is dipped in 0.1 M copper sulphate solution at 25°C. Calculate the electrode potential of copper.
[Given: $\ce{E^0_{{Cu^{2+}|Cu}}}$ = 0.34 V]

Evaluation | Q 22. | Page 67

For the cell $\ce{Mg_{(s)}|Mg^{2+}_{( aq)}||Ag^+_{( aq)}|Ag_{(s)}}$, calculate the equilibrium constant at 25°C and maximum work that can be obtained during operation of cell.
Given: $\ce{E^0_{{Mg^{2+}|Mg}}}$ = −2.37 V and $\ce{E^0_{{Ag^{+}|Ag}}}$ = 0.80 V

Evaluation | Q 23. | Page 67

8.2 × 1012 litres of water is available in a lake. A power reactor using the electrolysis of water in the lake produces electricity at the rate of 2 × 106 Cs−1 at an appropriate voltage. How many years would it like to completely electrolyse the water in the lake? Assume that there is no loss of water except due to electrolysis.

Evaluation | Q 24. | Page 67

Derive an expression for the Nernst equation.

Evaluation | Q 25. | Page 67

Write a note on sacrificial protection.

Evaluation | Q 26. | Page 67

Explain the function of H2 – O2 fuel cell.

Evaluation | Q 27. | Page 67

Ionic conductance at infinite dilution of Al3+ and $\ce{SO^{2-}_4}$ are 189 and 160 mho cm2 equiv−1. Calculate the equivalent and molar conductance of the electrolyte Al2(SO4)3 at infinite dilution.

Evaluation

## Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Chemistry Volume 1 and 2 Answers Guide chapter 9 - Electro Chemistry

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Concepts covered in Class 12th Chemistry Volume 1 and 2 Answers Guide chapter 9 Electro Chemistry are Variation of Molar Conductivity with Concentration, Conductivity of Electrolytic Solution, Electrochemical Cells, Thermodynamics of Cell Reactions.

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