CBSE Class 12 Chemistry Electrochemistry Worksheet Set D

CBSE Class 12 Chemistry Electrochemistry (1). Students can download these worksheets and practice them. This will help them to get better marks in examinations. Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

1. The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called ___________.

2. Under what condition an electrochemical cell can behave like an electrolytic cell ?

3. What is the quantity of charge in faraday is required to obtain one mole of aluminum from Al2O3 ?

4. How the cell constant of a conductivity cell changes with change of electrolyte, concentration and temperature?

5. What will happen at anode during the electrolysis of aqueous solution of CuSO4 in the presence of Cu electrodes?

6. Under what condition is ECell = 0 or ΔrG = 0 ? OR Give the condition for Daniell Cell in which there is no flow of electrons or current.

7. Why is alternating current used for measuring resistance of an electrolytic solution?

8. How will the pH of brine (aq. NaCl solution) be affected when it is electrolyzed ?

9. Unlike dry cell, the mercury cell has a constant cell potential throughout its useful life. Why?

10. Mention the purpose of salt-bridge placed between two half-cells of a galvanic cell?

11. Two metals A and B have electrode potential values of – 0.25V and 0.80V respectively. Which of these will liberate hydrogen gas from dilute H2SO4 ?

12. What is the effect of temperature on molar conductivity?

13. What is the role of ZnCl2 in the dry cell ?

14. Why is the equilibrium constant K, related to only E° cell and not Ecell ?

15.Rusting of iron is quicker in saline water than in ordinary water. Why is it so?

16. Why rusting of iron prevented in alkaline medium?

1. The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called ___________.

2. Under what condition an electrochemical cell can behave like an electrolytic cell ?

3. What is the quantity of charge in faraday is required to obtain one mole of aluminum from Al2O3 ?

4. How the cell constant of a conductivity cell changes with change of electrolyte, concentration and temperature?

5. What will happen at anode during the electrolysis of aqueous solution of CuSO4 in the presence of Cu electrodes?

6. Under what condition is ECell = 0 or ΔrG = 0 ?

OR Give the condition for Daniell Cell in which there is no flow of electrons or current.

7. Why is alternating current used for measuring resistance of an electrolytic solution?

8. How will the pH of brine (aq. NaCl solution) be affected when it is electrolyzed ?

9. Unlike dry cell, the mercury cell has a constant cell potential throughout its useful life. Why?

10. Mention the purpose of salt-bridge placed between two half-cells of a galvanic cell?

11. Two metals A and B have electrode potential values of – 0.25V and 0.80V respectively. Which of these will liberate hydrogen gas from dilute H2SO4 ?

12. What is the effect of temperature on molar conductivity?

13. What is the role of ZnCl2 in the dry cell ?

14. Why is the equilibrium constant K, related to only E° cell and not Ecell ?

15.Rusting of iron is quicker in saline water than in ordinary water. Why is it so?

16. Why rusting of iron prevented in alkaline medium?

17. 1 mole KCl dissolved in 500 cc of the solution, Due to more mobility of ions and more degree of dissociation.

18. Recharging is possible in this case because PbSO4 formed during discharging is a sticky solid which sticks to the electrode. Therefore it can either take up or give up electrons during recharge.

19. Bisphenol

20. Coulomb/ mol

ELECTROCHEMISTRY

TWO Marks Each

1.Solutions of two electrolytes ‘A’ and ‘B’ are diluted. The Λm of ‘B’ increases 1.5 times while that of A increases 25 times. Which of the two is a strong electrolyte? Justify your answer.

2. When acidulated water (dil.H2SO4 solution) is electrolysed, will the pH of the solution be affected? Justify your answer.

3. What advantage do the fuel cells have over primary and secondary batteries?

4. How does the density of the electrolyte change when the lead storage battery is discharged ?

5. Why on dilution the Λm of CH3COOH increases drastically, while that of CH3COONa increases gradually?

6. What is the relationship between Gibbs free energy of the cell reaction in a galvanic cell and the emf of the cell? When will the maximum work be obtained from a galvanic cell?

7.Define corrosion. Write chemical formula of rust.

8.Can you store copper sulphate solutions in a zinc pot?

9.Write the cell reaction which occur in the lead storage battery

(a) when the battery is in use (b) when the battery is on charging.

10.Write the product of electrolysis of aqueous copper sulphate by using platinum electrode. Answer

1.Electrolyte ‘B’ is strong as on dilution the number of ions remains the same, only interionic attraction decreases therefore increase in ∧ is small.

2.pH of the solution will not be affected as[ H+] remains constant.

Important Questions for NCERT Class 12 Chemistry Electrochemistry 

Question. Standard free energies of formation (in kJ/mol) at 298 K are –237.2, –394.4 and –8.2 for H₂O(l), CO₂(g) and pentane(g) respectively. The value of E°cell for the pentane-oxygen fuel cell is
(a) 1.0968 V
(b) 0.0968 V
(c) 1.968 V
(d) 2.0968 V 

Question. The equilibrium constant of the reaction :
Cu(s) + 2Ag⁺_(aq) → Cu²⁺(aq) + 2Ag(s);
E° = 0.46 V at 298 K is
(a) 2.0 × 10¹⁰
(b) 4.0 × 10¹⁰
(c) 4.0 × 10¹⁵
(d) 2.4 × 10¹⁰ 

Question. The standard e.m.f. of a galvanic cell involving cell reaction with n = 2 is found to be 0.295 V at 25°C.
The equilibrium constant of the reaction would be
(a) 2.0 × 10¹¹
(b) 4.0 × 10¹²
(c) 1.0 × 10²
(d) 1.0 × 10¹⁰
(Given F = 96500 C mol–1, R = 8.314 J K^–1 mol^–1)

Question. On the basis of the information available from the reaction, 4/3Al + O₂ → 2/3Al₂O₃, ΔG = –827 kJ mol^–1 of O₂, the minimum e.m.f. required to carry out an electrolysis of Al2O3 is (F = 96500 C mol^–1)
(a) 2.14 V
(b) 4.28 V
(c) 6.42 V
(d) 8.56 V 

Question. For the disproportionation of copper
2Cu⁺ → Cu²⁺ + Cu, E° is (Given : E° for Cu²⁺/Cu is 0.34 V and E° for Cu²⁺/Cu+ is 0.15 V)
(a) 0.49 V
(b) –0.19 V
(c) 0.38 V
(d) –0.38 V

Question. E° for the cell, Zn | Zn²⁺_(aq) ||Cu²⁺_(aq) | Cu is 1.10 V at 25°C, the equilibrium constant for the reaction
Zn + Cu²⁺ _(aq) → Cu + Zn2+
(aq) is of the order
(a) 10⁺¹⁸ 
(b) 10⁺¹⁷
(c) 10^–28 
(d) 10⁺³⁷

Question. The molar conductivity of a 0.5 mol/dm³ solution of AgNO₃ with electrolytic conductivity of 5.76 × 10^–3 S cm^–1 at 298 K is
(a) 2.88 S cm²/mol
(b) 11.52 S cm²/mol
(c) 0.086 S cm²/mol
(d) 28.8 S cm²/mol

Question. At 25 °C molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is 9.54 ohm^–1 cm² mol^–1 and at infinite dilution its molar conductance is 238 ohm^–1 cm² mol^–1. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is
(a) 4.008%
(b) 40.800%
(c) 2.080%
(d) 20.800% 

Question. Limiting molar conductivity of NH₄OH [i.e., L°m(NH₄OH)] is equal to
(a) L°m(NH₄Cl) + L°m(NaCl) – L°m(NaOH)
(b) L°m(NaOH) + L°m(NaCl) – L°m(NH₄Cl)
(c) L°m(NH₄OH) + L°m(NH₄Cl) – L°m(HCl)
(d) L°m(NH4Cl) + L°m(NaOH) – L°m(NaCl)

Question. Molar conductivities (L°m) at infinite dilution of NaCl, HCl and CH₃COONa are 126.4, 425.9 and 91.0 S cm² mol^–1 respectively. (L°m) for CH₃COOH will be
(a) 425.5 S cm² mol^–1
(b) 180.5 S cm² mol^–1
(c) 290.8 S cm² mol^–1
(d) 390.5 S cm² mol^–1

Question. An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to
(a) increase in ionic mobility of ions
(b) 100% ionisation of electrolyte at normal dilution
(c) increase in both i.e., number of ions and ionic mobility of ions
(d) increase in number of ions.

Question. The equivalent conductance of M/32 solution of a weak monobasic acid is 8.0 mho cm2 and at infinite dilution is 400 mho cm². The dissociation constant of this acid is
(a) 1.25 × 10^–6
(b) 6.25 × 10^–4
(c) 1.25 × 10^–4
(d) 1.25 × 10^–5

Question. Kohlrausch’s law states that at
(a) infinite dilution, each ion makes definite contribution to conductance of an electrolyte whatever be the nature of the other ion of the electrolyte
(b) infinite dilution, each ion makes definite contribution to equivalent conductance of an electrolyte, whatever be the nature of the other ion of the electrolyte
(c) finite dilution, each ion makes definite contribution to equivalent conductance of an electrolyte, whatever be the nature of the other ion of the electrolyte
(d) infinite dilution each ion makes definite contribution to equivalent conductance of an electrolyte depending on the nature of the other ion of the electrolyte. 

Question. Equivalent conductances of Ba²⁺ and Cl^– ions are 127 and 76 ohm^–1 cm^–1 eq^–1 respectively. Equivalent conductance of BaCl₂ at infinite dilution is
(a) 139.5
(b) 101.5
(c) 203
(d) 279

Please click the link below to download CBSE Class 12 Chemistry Electrochemistry (1)