Aqa chem 4/ chem 5 june 2016 thread

E Au+(/Au) > E O2(/H2O)
So H2O reduces Au+ ions to Au so they are not normally found in aqueous solutions.
Combine Half Equation 1 and 2 (Times 1st one by 2) to get:
2Au+ + H2O → 2Au + 1/2O2 + 2H+

http://www.cram.com/flashcards/transition-metal-complexes-colours-6839469
I made these.
I haven't written solution or precipitate on all of them and some of them may say precipitate instead of solution. But the one's with charges are solutions and the ones without are precipitates

Know the 4 precipitation reactions

Let x be (H2O)6

Cux pale blue
Cox pale pink
Fe2+x pale green
Fe3+ yellow

Cu(oh)2 blue
Cu(oh)2 blue
Fe(oh)2 green
Fe(oh)3 orange

Cucl4 yellow
Cocl4 blue

Cu(nh3)4(h2o)2 deep blue

Kmno4 oxidizing agent is purple and turns. Colour less at end point

Acidified potass di chrome

Orange to green

thnx! ive memorized most of these just some odd balls like the chloride complexes. also it says on the quiz that fe(h20)6^3+ is pale violet but i swear its yellow? or am i reading it wrong?

You don't need every colour spec specifically states fe cu and co in ppt reactions and cu nh3 deep blue cucl4 and cocl4

I dont get the E cell greater than the other one stuff

Same with 7c.
Do you mind explaining

Someone help please
Why do you x2 for -348 and not 158?
Question 1biii in June 2010 paper

Mark scheme: http://filestore.aqa.org.uk/subjects/AQA-CHEM5-W-MS-JUN10.PDF


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like every possible colour? im more than willing to learn every colour on the spec but i dont really have a source to study them, revision guide doesnt give them all and i cant find a useful site. Do you have any recommendations?

Getting hella nervous now :/// I feel like I know everything but I feel like I'm just going to blank in the exam

The electrode potentials can show how one thing would react with another. If one is more +ve than the other then that will be the oxiding agent and the other (the more negtaive one) will be the reducing agent. So the reaction here is that Water will reduce the Au+ ions to a solid Au. So they will be a ppt in water and not in an aqueous solution whch implies that it dissolved in water which is not the case.

Its yellow

https://chemrevise.files.wordpress.com/2016/05/mod-5-revision-guide-4-transition-metals.pdf

scroll to bottom.

You require two F(g) and this produced from the equation given and this is +158
The equation with -348 is PER F to F- and as you need 2, you need to multiply it by 2.
Hope that helped

Same lol. But I really can't afford to screw up this exam after chem 4, which makes me 10x even more nervous


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I see, but in the equation how do you know which species is the oxidising agent. Is it because itself gets reduced so Au+ goes to Au?

And the reducing agent would be H2O because it gets oxidised to H+?