AQA CHEM5 A2 Chemistry - 19th June 2013

Guys how would you do question 4biv and 4c??? and 5bii and 5cii???
i have no ideaaa

Well when you're writing cell representations, the most positive electrode goes on the right. The reduced species go furthest away from the salt bridge and the oxidised species go closest to the salt bridge. You're told you have to use platinum contacts. Since all of the species are aqueous, you can use commas to separate them instead of lines

Pt | SO₃^2-_(aq), SO₄^2-_(aq) || ClO₃^-_(aq), Cl^-_(aq) | Pt

When you're writing overall equations, you always reverse the half-equation with the lower E value i.e.
ClO₃^- + 6H⁺ + 6e^- $\rightarrow$ Cl^- + 3H₂O
SO₃^2- + H₂O $\rightarrow$ SO₄^2- + 2H⁺ + 2e^-

Then just combine them as you usually would:
ClO₃^- + 3SO₃^2- $\rightarrow$ Cl^- + + 3SO₄^2-

ClO₃^- is reduced, so it must be the oxidising agent. SO₃^2- is oxidised, so it must be the reducing agent

Hopefully I've done everything right. If you need anything explained just quote me

Just done another past paper. 90/100

Need to go over the explanation for the colours 'cause I keep losing a mark on that. Need to work on the explanation on why a reaction will not be feasible when you increase/decrease temp. I understand the whole thing but I'm not hitting the marks

that was part of the legacy spec, synoptic stuff was required. Not for us

When writing cell representations, when you write what the electrodes are made of? Also, when is it just platinum?

Are you sure?I thought this module was synoptic too?

In the june 12 paper how are you supposed to know the reaction between phosphoric acid and magnesium oxide? Qs 1e(i) if anyone wants to take a look

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You're supposed to know how each p3 reacts as an acid or base

Yeah but this is a reaction with an oxide which is neither an acid nor a base

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