CBSE Class 12 Chemistry Electrochemistry Questions Answers

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ONE Mark Each

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 E_Cell = 0 or Δ_rG = 0 ? OR Give the condition for Daniel 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 E_cell ?

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. Which will have greater molar conductivity and why?

    1 mole KCl dissolved in 200 cc of the solution OR 1 mole KCl dissolved in 500 cc of the solution.

18. Why Lead storage battery as a secondary cell can be recharged?

19. Write the name of a chemical substance which is used to prevent corrosion.

20. Write the unit of Faraday constant. \

21. Can you store CuSO₄ solution in Zn pot ?

22. Write the name of electrolyte used in mercury cell.

23. What does the negative value of E⁰cell indicate?

24. What flows in the internal circuit of the Galvanic cell?

25. What is the EMF of the cell when the cell reaction attains equilibrium?

26. Why does an aqueous solution of NaCl in electrolysis give H₂ gas at cathode not sodium metal?

27. Which type of metal can be used in cathodic protection of iron against rusting?

28. Why does the conductivity of solution decreases on dilution?

29. Except hydrogen, write the name of two chemical species which are used in fuel cell.

30. How many coulombs are required for conversion of 1 mol FeO into Fe₂O₃?

31. State the factors which influence the value of cell potential.

32. What is the relationship between the free energy change and EMF of the cell?

33. What are the products of electrolysis of molten NaCl and aqueous solution of NaCl?

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

35. Rusting of iron is quicker in saline than ordinary water. Why?

36. Write one use of Kohlrausch’s law.

37. What is cell constant?

38. What is the relationship between Molar conductivity of electrolytic solution to its degree of dissociation?

39. Which type of cell is used in wrist watch?

40. Which acid does not react with rust? 

Three marks question:-

1. Explain construction and working of standard Hydrogen electrode?

2. What is an electrochemical series? How does it predict the feasibility of a certain redox reaction?

3. The conductivity of an aqueous solution of NaCl in a cell is 92.1 cm-1 the resistance offered by this cell is 247.8. Calculate the cell constant?

4. The measured resistance of a cell containing 7.5 x 10-3 M solution of KCl at 250C was 1005 Ω Calculate

(a) Specific conductance and

(b) Molar conductance of the solution. Cell Constant = 1.25 cm-1

5. Enlist the factors affecting corrosion?

Answer of one mark:-

1. Cell emf

2. When E_ext> _Ecell

3. 3F

4. Remain unchanged for a cell

5. Copper will dissolve at anode

6. When the cell reaction reaches equilibrium

7. Alternating current is used to prevent electrolysis so that concentration of ions in the solution remains constant. Otherwise if DC is used the ions will get discharged and electrolysis will occur

8. The pH of the solution will rise as NaOH is formed in the electrolytic cell.)

9. Ions are not involved in the overall cell reaction of mercury cells.

10. Neutralize the two half cell.

11. Metal - A

12. Molar conductivity of an electrolyte increases with increase in temperature.

13. ZnCl₂ absorbs ammonia produced in the reaction by forming a complex [Zn(NH₃)₄]²⁺

14. This is because E cell is zero at equilibrium. 

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