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# Half Equations watch

1. I just wondered if a chemistry genius out there could quickly explain these for me. I've never really understood them! I do AQA Modular Triple award btw!
2. Its for electrolysis. The liquid (or aqueous solution) is basically the two ions (positive and negative) floating in water (kind of). The one ion goes to an electrode and the other to the other electrode. The half equations are just what goes on at each one instead of as a whole.
3. If you are given the mass of the product at one electrode, how do you work out the mass made at the other electrode?? That's what I don't get.
4. I think Electrolysis Half Equations are the hardest things to learn in Chemistry, even out of the Contact Process etc etc... My chem teacher told me to "self learn" the 1/2 equations topic; probably 'cos he didn't understand it!

Anyway, i've said: "forget them, focus on the other stuff", they may only be worth a couple of marks.
5. Well in answer to Excalibur's question, you do as follows: (I'm pretty sure this is triple stuff though)

Basically you work out the no. of moles of that substance that was evolved by doing mass/RAM.
Then you see what charge the ion of that substance has. e.g. K+, H+, Cl- etc.
Then you see what is discharged at the other electrode, and compare its charge to the substance who's mass you know. If the charge is the same, the same number of moles will be evolved; if its double the charge HALF the number of moles will be evolved etc. So you find out how many moles are discharged and then multiply this by the RAM to give the mass.

Hope this helps
6. (Original post by excellent_em)
Well in answer to Excalibur's question, you do as follows: (I'm pretty sure this is triple stuff though)

Basically you work out the no. of moles of that substance that was evolved by doing mass/RAM.
Then you see what charge the ion of that substance has. e.g. K+, H+, Cl- etc.
Then you see what is discharged at the other electrode, and compare its charge to the substance who's mass you know. If the charge is the same, the same number of moles will be evolved; if its double the charge HALF the number of moles will be evolved etc. So you find out how many moles are discharged and then multiply this by the RAM to give the mass.

Hope this helps
OK, I think I understand... would you be able to go through it with an example at all?
7. yes an example would be best

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Updated: June 13, 2006
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