Answer:
Mass of copper deposited = 31.75 g
Step-by-step explanation:
According to Faraday's second law of electrolysis, when the same quantity of electricity is passed through different electrolytes, the relative number of moles of the elements deposited are inversely proportional to the charges on the ions of the elements.
From this law, it can be seen that the higher the charge, the lower the number of moles of a given element deposited.
Number of moles of aluminium in 9 g of aluminium = mass / molar mass
Molar mass of aluminium = 27 g
Number of moles of aluminium = 9/27 = 1/3 moles
Charge on aluminium ion = +3
3 moles of electrons will discharge 1 mole of aluminium,
1 mole of electrons will discharge 1/3 moles of aluminium
Number of moles of electrons involved = 1 mole of electrons
Charge on copper ion = +2
1 mole of electrons will discharge 1/2 moles of copper.
Mass of 1/2 moles of copper = number of moles × molar mass of copper
Molar mass of copper = 63.5 g
Mass of copper deposited = 1/2 × 63.5 = 31.75 g