Topic Content:
- Theory Questions and Answers – Electrolysis II
Theory Questions – Electrolysis II
1. (a) Sketch to illustrate Faraday’s first law of electrolysis.
(b) Describe how you investigate Faraday’s first law of electrolysis using copper(II) tetraoxosulphate(VI) solution and copper electrodes.
2. Calculate the number of Faraday’s of electricity required to liberate:
(a) 16.2 g of silver
(b) 14.3 g of aluminum
(c) 2.24 dm3 of oxygen gas at STP
(d) 0.23mole of hydrogen molecule
[Ag = 108, Al = 27, molar volume = 22.4 dm3 at stp]
3. Determine the mass of copper deposited by 4.0 moles of electrons in the reaction represented by the equation: Cu2+ + 2e– → Cu(s) [Cu = 64]
4. How long would it take to deposit 0.08 g of copper from CuCl2 solution by passing a current of 0.5 A?
[Cu = 64, 1F = 96500 C]
5. The following data were recorded in an experiment on electrolysis:-
Table: Data recorded in an experiment on electrolysis
| S/N | Current (AMPs) | Time of current flow (sec) | Quantity of electricity (c) | Mass of metal (z) deposited (g) |
| A | 0.5 | 300 | ______ | 0.25 |
| B | 0.5 | 600 | ______ | 0.65 |
| C | 0.5 | _______ | 375 | 0.85 |
| D | 0.5 | ________ | 480 | 1.30 |
| E | 0.5 | 1500 | _______ | 1.38 |
| F | 0.5 | 1800 | _________ | 2.28 |
(a) Copy and complete the table above by calculating the time or quantity of electricity passed in each reaction.
(b) Plot the graph of the mass of Z deposited against the quantity of electricity passed
(c) From your graph
(i) How long will it take for the same quantity of electricity to deposit 0.35g of Z?
(ii) Calculate the mass of Z that was deposited by 0.5 A for 27 mins 30 secs
(iii) What is the quantity of electricity when 1.25 g of the metal is deposited?
(iv) Determine:
- the electrochemical equivalent
- Chemical equivalent
(v) Which of Faraday’s laws of electrolysis does this experiment Obey? give the reasons for your answer
6. In the electrolysis of nickel chloride using carbon electrodeElectrodes are conductors, in the form of wires, rods or plates, through which current enters and leaves the electrolyte. When the current leaves the electrodes it is known as the cathode... More, 9.5 g of Nickel was deposited on the cathodeA cathode is the electrode from which a conventional current leaves the electrolyte. It is the negative part of the cell where reduction takes place. More electrode. What volume of oxygen will be liberated at STP?
[Ni = 59, if = 96500 C, molar volume = 22.4 d/m3 at stp]
7. Two electrolytic cells containing sodium salt and copper salt electrolytes respectively are connected in series.
A current of 2 Amperes is passed for 30 min. calculate the mass of copper deposited [Na = 23, Cu = 64, 1F = 96500 C]
8. (a) state the following:
(i) Faraday’s first law of electrolysis
(ii) Faraday’s second law of electrolysis
(b) State three applications of electrolysis
(c) A student was asked to electroplate a stainless steel spoon using a brass rod as the electrode and copper (ii) tetraoxosulphate (vi) solution as electrolyteAn electrolyte is a substance that dissociates in water into charged particles called ions. Positively charged ions are called cations. Negatively charged ions are called anions. Simply, an electrolyte is a... More.
The following were the results he obtained
Mass of spoon = 107.55 g
Mass of copper-coated spoon = ?
Mass of brass rod = 50.4g
Current = 0.45 A
Time taken = 28 min
(i) Draw a diagram of the setup the student used to electroplate the spoon
(ii) Which electrode should be the spoon?
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