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Redox

Got 2 chemistry units to do in the summer so I thought I'd do some revision, by doing past papers.

But what I discovered last night was that i know **** all about Redox, couldn't do a single question on it.

I know what an oxidising / reducing agent is but I don't get how to work out what the charges are.

For example, one of the question was:
Write an ionic equation for the reaction between silver nitrate and the halid ion you identified above (chloride)


How would I go about this sorta question? I'm sure I missed a lesson or two on this (or just never bothered to listen in class XD)
1. Write out the full chemical equation including state symbols
2. Split up the aqueous species into ions
3. Cancel ions that appear on both sides

:smile:
Reply 2
Avatar for Andylol
Andylol
OP
14
EierVonSatan
1. Write out the full chemical equation including state symbols
2. Split up the aqueous species into ions
3. Cancel ions that appear on both sides

:smile:


AgNO3 + Cl => AgCl + NO3

That's pretty much all I can do (Not even sure if that's right)

=[
Reply 3
Avatar for xSkyFire
xSkyFire
19
Andylol
Got 2 chemistry units to do in the summer so I thought I'd do some revision, by doing past papers.

But what I discovered last night was that i know **** all about Redox, couldn't do a single question on it.

I know what an oxidising / reducing agent is but I don't get how to work out what the charges are.

For example, one of the question was:


How would I go about this sorta question? I'm sure I missed a lesson or two on this (or just never bothered to listen in class XD)



Ag+ + Cl- = AgCl

Unfortunately redox is one of the topics that comes with experience, it'd be easy if there was a trick to it but all the elements of the different groups have annoying properties to work with. Sulphur comes in so many oxidation states, there are superoxides too to consider...

The most basic rule is the ion will form depending on it's group number, group one is +1 ions, Na+, K+ etc.

Group 2 is Mg2+, Ba2+, etc. Then as you get the Aluminium and some others it starts to get more tricky, the halogens such as chlorine can disproportionate in water to give a starting 0 oxidation state, then a +1 and a -1 which I think you may need to know.

It just comes with practice really, you'll have to really know your chemistry to know what's going on but the entire paper won't be on redox, probably 4 or 5 marks at the most.
1. AgNO3(aq) + Cl-(aq) ---> AgCl(s) + NO3-(aq)
2. Ag+(aq) + NO3-(aq) + Cl-(aq) ---> AgCl(s) + NO3-(aq) silver nitrate dissociates in water to give aqueous ions
3. Ag+(aq) + Cl-(aq) ---> AgCl(s) nitrate ions cancel
Reply 5
Avatar for xSkyFire
xSkyFire
19
Also the one you posted would get you 0 marks, that's not an ionic equation because you included the spectator ions XD

Only include ions that you want in your final product and usually water if that's included.
Reply 6
Avatar for Andylol
Andylol
OP
14
>_< What's a spectator ion
Reply 7
Avatar for xSkyFire
xSkyFire
19
An Ion that doesn't actually take part in the reaction you're looking at. The ionic equation between silver ions and iodide ions wouldn't include nitrate ions XD

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