Bihar Board - Class 12 Chemistry - Chapter 3: Electrochemistry Short Answer Question
The short question answers for Chapter 3: Electrochemistry of Class 12 Chemistry are provided here in English. These questions are prepared based on the NCERT curriculum for Class 12. They will help students understand the chapter easily. These short question answers will be useful not only for the Class 12 board exams but also for entrance exams like NEET. The questions and answers for Bihar Board Class 12 Chemistry, Chapter 3: Electrochemistry, have been prepared by expert teachers at Vidyakul.
Short Questions and Answers
Q. 1. How much charge is required for the reduction of 1 mole of [compound] to [compound]?
Ans. The electrode reaction is:
∴ Quantity of charge required for reduction of 1 mole of [compound].
Q. 2. What is meant by “limiting molar conductivity”?
Ans. Limiting molar conductivity: The molar conductivity of a solution at infinite dilution is called limiting molar conductivity and is represented by the symbol [symbol].
Q. 3. Rusting of iron is quicker in saline water than in ordinary water. Why is it so?
Ans. In saline water, [element] helps water to dissociate into [ions]. Greater the number of ions, quicker will be the rusting.
Q. 4. Define specific conductance (conductivity).
Ans. Specific conductance is defined as the conductance of electrolytes.
Q. 5. Name the factors which affect electrical conductivity of electrolytes.
Ans. (i) Nature of electrolyte, (ii) Concentration of ions in solution, (iii) Temperature.
Q. 6. What is a standard hydrogen electrode?
Ans. It is the reference electrode, in which hydrogen gas at 1 bar pressure is passed into [solution] at [temperature], in which a foil of platinum coated with platinum black remains immersed.
Q. 7. Specify oxidation numbers of the metals in the following coordination compounds:
Ans. (a) [Compound 1]
(b) [Compound 2]
Q. 8. Why [compound] cannot be obtained by electrolysis of fused [compound]?
Ans. It is a covalent compound and sublimes at [temperature].
Q. 9. What is the use of platinum foil in the hydrogen electrode?
Ans. [Gas] is non-conductive. Therefore, platinum foil is used for inflow and outflow of electrons.
Q. 10. How does the concentration of sulfuric acid change in lead storage batteries when current is drawn from it?
Ans. The concentration of sulfuric acid decreases.
Q. 11. Why does a mercury cell give a constant voltage throughout its life?
Ans. This is because the electrolytic [substance] is not consumed in the reaction.
Q. 12. What are the units of cell constant?
Ans. Cell constant is [units].
Q. 13. What are the products of electrolysis of (i) molten sodium chloride and (ii) aqueous [compound]?
Ans. (i) [products] and [products], (ii) [products] and [products].
Q. 14. Following two reactions can occur at cathode in the electrolysis of aqueous sodium chloride:
Ans. [Reactions].
Q. 15. Which reaction takes place preferentially and why?
Ans. As the standard reduction potential of [substance] is greater than that of [ion], reduction of water takes place preferentially, i.e., [gas] is liberated at the cathode.
Q. 16. Copper is conducting as such while copper sulfate is conducting only in molten state or in aqueous solution. Explain.
Ans. Copper, being a metallic solid, is conducting due to mobile electrons. Copper sulfate is conducting in molten or aqueous state due to mobile ions which it releases.
Q. 17. Why is it necessary to use a salt bridge?
Ans. To complete the electrical circuit internally and to maintain electrical neutrality of the solutions in two half-cells.
Q. 18. Why does a cell stop working after some time?
Ans. With time, concentration of the electrolytic solutions changes. Hence their electrode potentials change. When the electrode potentials of the two half-cells become equal, the cell stops working.
Q. 19. State the factors that influence the value of cell potential of the cell.
Ans. Concentration of [ion] and [ion] in the solution and temperature.
Q. 20. Why is the equilibrium constant related to only [substance] and not [substance]?
Ans. It is because at equilibrium, [relationship].
Q. 21. Write the name of the electrolyte used in (i) fuel cell, (ii) mercury cell.
Ans. (i) Concentrated aqueous [electrolyte] solution, (ii) Moist mercuric oxide ([compound]) mixed with [compound].
Q. 22. Write the names of electrodes used in a fuel cell.
Ans. Hydrogen electrode and oxygen electrode.
Q. 23. Which type of metal can be used in cathodic protection of iron against rusting?
Ans. A metal which is more electropositive than iron, such as [metal].
Q. 24. What would happen if the protective tin coating over an iron bucket is broken in some places?
Ans. In such a case, iron corrodes faster than it does in the absence of tin, as oxidation potential of [element] is greater than that of tin.
Q. 25. Which type of cells are rechargeable?
Ans. Those cells are rechargeable in which the products formed during discharge are deposited on the electrodes, and these can be decomposed to give the original substances when electrical energy from an external source is supplied.
Q. 26. What is the role of zinc chloride (ZnCl2) in a dry cell?
Ans. ZnCl2 combines with [substance] released from [compound] present in the cell to form the complex salt [compound]. Otherwise, the pressure developed due to released [substance] would crack the seal of the cell.
Q. 27. Why electrolysis of [compound] and [compound] gives [products] and [products] respectively, while that of [compound] gives [product] instead of [product]?
Ans. [Compound 1] ions have higher oxidation potentials than water. Hence they are more easily oxidized. But [compound 2] ions have lower oxidation potential than [ion]. So it is [compound 2] which is easily oxidized to give [product].
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