Electroysis Q

[sandi]

In the production of copper and aluminium by electrolysis, when the same quantity of electricity is passed through the cells, the simplest ratio of the mass of copper deposited compared to the mass of aluminium deposited would be?

[Tomanomanous]

We look at the question first. As we know the same electricity passed through each electrolytic cell, the same number of electrons passed through.
We then look at our electrochemical series and notice the following:

Cu2+  plus   2e- makes Cu
Al3+  plus  3e- makes Al

According to our equations, Copper consumes two electrons to go from an aqueous ion to a solid.
Aluminium consumes three electrons to go from an aqueous ion to a solid.

They both are only given the same number of electrons. Aluminium needs 1.5 times more electrons. So 1.5 more moles of Copper is going to be made compared to Aluminium.
Mole ratio of copper:aluminium is 3:2

If it's asking for mass, I'd imagine you multiply the mole ratio by each elements respective molar mass like so
3*Molar mass of Copper :: 2*Molar mass of Aluminium
3*63.5:2*27
190.5:54

I hope I'm right ahaha. I'm not sure if I am but that's how I'd approach it.