1. Quantitative Electrolysis

2. Electrolysis
When performing electrolysis reactions it is often desirable to calculate how much substance is being produced, what length of time is required for reaction, what size current is needed etc. These calculations require a knowledge of Faraday’s Laws. These may be stated generally: The mass of any substance deposited, evolved, or dissolved at an electrode in an electrochemical process is directly proportional to the amount of electricity passed through the cell. For one mole of a substance to be deposited, evolved, or dissolved at an electrode, the passage of one, two, three or another whole number of moles of electrons is required.

3. Calculations are based on the relationship relating n(e-) and mass
The amount of charge carried by one mole of electrons is C. (Data Book value states this value)
This is called one faraday of charge.
  𝑛(𝑒–) = 𝑄 𝐹 = 𝐼𝑡 𝐹 , where   
I = current (amps) t = time (secs)
Q = charge (coulombs) F = Faraday (C/mol)

4. If the equation for the reaction at an electrode is known, and the number of mole of electrons involved, then the number of moles of substance reacting is easily calculated. Complete the Quantitative Electrolysis questions (up to Q8)

5. Question 1
What mass of copper is produced if copper (II) nitrate solution is electrolysed for 10 minutes using a current of 2.0 amps?
(b) What volume of gas would also be produced at S.L.C?

6. Question 2
What time is needed if a current of 1.0 amp is passed through a solution of nickel(II) nitrate and 0.50g of metallic nickel is produced?

7. Determination of the Avogadro Constant
One simple application of quantitative electrolysis is to determine the Avogadro Constant (NA).
If the number of coulomb of charge required to produce a known mass of metal from solution is known, then the number of coulomb associated with one mole of metal is easily found.
The charge on one electron is known:
e– = ×10−19 Coulomb ( 𝐹 𝑁𝐴 )
  (this value is in the data book)
From these two pieces of information, a value for NA can be easily found.
Now try Q9 and 10 from the question booklet