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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: hyperblade01 on November 07, 2009, 12:40:59 pm

Title: Cells
Post by: hyperblade01 on November 07, 2009, 12:40:59 pm

(http://i167.photobucket.com/albums/u128/hyperblade01/2009tssmchem.png)

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?

Title: Re: Cells
Post by: lukeperry91 on November 07, 2009, 12:44:47 pm

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

Title: Re: Cells
Post by: hyperblade01 on November 07, 2009, 01:03:43 pm

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

Title: Re: Cells
Post by: arthurk on November 07, 2009, 01:50:14 pm

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

Title: Re: Cells
Post by: Jarzoon on November 07, 2009, 01:57:42 pm

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 :P

bii) biii) spot on.

Title: Re: Cells
Post by: Jarzoon on November 07, 2009, 02:03:35 pm

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.

Title: Re: Cells
Post by: hyperblade01 on November 07, 2009, 02:53:23 pm

Quote from: Jarzoon on November 07, 2009, 01:57:42 pm

Basic physics knowledge required here but yeah :P

=.=

Thanks!

Title: Re: Cells
Post by: Dark Horse on November 07, 2009, 04:36:41 pm

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?

Title: Re: Cells
Post by: Jarzoon on November 07, 2009, 04:44:23 pm

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

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