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Question
Answer the following:
How will you calculate the moles of electrons passed and mass of the substance produced during electrolysis of a salt solution using reaction stoichiometry?
Solution
1) Calculation of moles of electrons passed:
Total charge passed is Q(C). The charge of one-mole electrons is 96500 coulombs (C). It is referred to as one faraday (I F). Hence,
Moles of electrons actually passed = `("Q"("C"))/(96500 ("C"// "mol e"^-))`
2) Calculation of moles of product formed:
The balanced equation for the half-reaction occurring at the electrode is devised. The stoichiometry of half reaction indicates the moles of electrons passed and the moles of the product formed. From this, we will find the mole ratio, which is given by:
Mole ratio = `"Moles of product formed in half-reaction"/"Moles of electrons required in half-reaction"`
Moles of product formed = Moles of electrons actually passed × mole ratio
`= ("Q"("C"))/(96500 ("C"// "mol e"^-)) xx "mole ratio"`
`= ("I"("A") xx "t"("s"))/(96500 ("C"// "mol e"^-)) xx "mole ratio"`
3) Mass of substance produced:
Mass of product (W) can be calculated as given below:
W = moles of product × molar mass of product
`= ("I"("A") xx "t"("s"))/(96500 ("C"// "mol e"^-)) xx "mole ratio" xx "molar mass of the product"`
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