When dealing with questions related to mole calculations, following a few simple steps can make it easier to solve them. 🤔
🤓Here is an example:
1.57 calculate the amounts of the products of the electrolysis of molten salts and aqueous solutions
One faraday is 96500 coulombs. It is also one mole of electrons.
If current of 0.2 Amps is passed through copper(II) sulphate for two hours, how much copper do you get?
Step 1:
Start by writing out the equation
Cu2+ + 2e → Cu
Step 2:
Find out the coulombs of electrons flowing
Charge (coulomb, C) = Current (ampere, A) × Time (second, s).
*Remember to convert the time into seconds !
Therefore, Charge = 0.2 × 7200 = 1440 coulombs
Step 3:
Convert Coulombs into moles of electrons
Moles = Coulombs / faraday
Moles = 1440/96500 = 0.015
Step 4:
Find the moles of the product using the scale factor
*From the equation, for every 2 moles of electrons, there will be 1 copper.
Scale factor = moles of product/moles of electrons = 1/2
Thus, there are 0.015 × 1/2 = 0.0075 moles of Cu
LAST STEP👏
Convert moles into mass
Mass = Moles × Molar Mass
The mass of Cu = 0.0075 × 63.5 = 0.48 g
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