Cells

[hyperblade01]

How do I determine the polarity? Do I have to be able to read that thing at the top with one vertical line being longer than the other?

For b), answers are:

i) 4, 4, 4 <<<<< because even though electrons are used, the same amount is released?
ii) 0, 0, 2 <<<<< 0 because (aq), water will be preferable and 2 because (l) and hence no water
iii) 4, 2, 2   <<<<< because of 2:1 ratio with mole electrons:copper

Is that correct reasoning?

[lukeperry91]

Use the electrochemical series bro its about the strength of the conjugate ox/reductants

[hyperblade01]

Could you please be more precise? Can a) be answered solely by using the series?

[arthurk]

It's electrolysis here as you're using a power supply thus the polarity of each electrode is determined by the power supply

[Jarzoon]

Yeah the longer branch indicates the Positive terminal of the power supply and so the electrons flow out of the shorter Negative branch. It's electrolysis so you should be able to determine which are the positive and negative electrodes.

bi) The same number of electrons pass through each cell because in a way it is a series circuit.
Since there is only one path for current in a series circuit, the same current must flow through each component of the circuit.
Basic physics knowledge required here but yeah

bii) biii) spot on.

[Jarzoon]

Oh also for bii) be careful because in an aqueous solution you can have preference over water if it's a stronger oxidant or a stronger reductant. Look at the electrochemical series.

[hyperblade01]

Basic physics knowledge required here but yeah

=.=

Thanks!

[Dark Horse]

with this question, what i was confused about was the whole Cu+ thing. That isnt even on the ECS, so how do you know that iw will or wotn react in preference to water?

[Jarzoon]

Yeah.. it's a bit dodgy. Lol maybe you can find some badass Enaught series in the exam

http://www.efunda.com/materials/corrosion/electrochem_list.cfm?sort=com