OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016)

Oh gosh not that.. Hoping they don't ask of calorimetry I mean they did have quite a hefty calculation question on it.

Ah ok. I need to go over it too. Lmao I'm going over so many stuff rn. The only green chemistry we have is the polymer stuff isn't it? So waste polymers you could make into other new polymer, sort and recycle, organic feedstock.

Test for sulfates is adding dilute HCl then BaCl and if a white precipitate forms a sulfate is present.
I can't remember the calorimetry test
Oxidation might ask about why we reflux (prevents the loss of volatile liquids by preventing the evapourated liquids from escaping by condensing them back).
Also about why we left the top open, which was to prevent explosions from pressure created by heating gas which would be danagerous if sealed by a stopper when condensing

yh I think so, also combustion for energy.
Good luck

Thank you! I still have another good 30 mins ahahah. Hmm maybe go over the synthetic routes. Is this likely to come up?

Ah so we do reflux so the vapours are condensed and returned to the vessel to ensure it undergoes full oxidation. As for the top open on what the test tube? Thats a really good point! Didn't think about that! Also the anti bumbing granules are to prevent against violent boiling.Which can then be easily filtered out.

Thank you! I still have another good 30 mins ahahah. Hmm maybe go over the synthetic routes. Is this likely to come up?

there was a longish question on that in the breadth, so i doubt it

I'm not sure, I don't think I'm gonna go over it

So if they give us a table of formation values to work out combustion, would you do products- reactants?! Or the other way around?

I didn't really know the synthetic routes that well so left that out..



Might go over disproportionation quickly now instead.

i think the main practical based questions that might come up is either qualitative analysis, titrations or purifying an organic liquid.
Titrations:
Preparing a standard solution-
1. Weigh out a particular mass of the solid.
2. Add it to a beaker.
3. Dissolve all of it in distilled water.
4. Add the solution to a 250cm3 volumetric flask.
5. Make up the solution to the graduation line (the bottom of the meniscus must be touching the graduation line)
6. Invert the flask several times to mix thoroughly.
Actual titration:
1. Take 25cm3 of the standard solution using a pipette and add it to the conical flask (this is because the concentration and volume of the standard solution is known).
2. Add the solution with the unknown concentration to the burette. Make sure the jet space of the burette is filled with the solution.
3. Add an indicator (eg.methyl orange which turns orange at end point or phenolphthalein which turns pink at endpoint)
4. Titrations the solutions approximately once until endpoint is reached to get an idea of the titre.
5. Repeat the titration several times to get several titres.
6. Calculate the mean titres by taking an average of concordant results (within 0.1 cm3 of each other)

i think that's all. Did i miss anything out?

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Thats a good idea. I think maybe the reaction with chlorine and water or chlorine and NaOH may come up

thank you so much

Products - reactants as formation values given

Yes thank you kiwi! I coudnt think of anything else to add. I mean they could ask extra questions like why use a white tile. Or why your answer may be less. Something about losing moles when transferring to the beaker? Erm add above the meniscus lowers the conectration? These are off the top of my head so could be wrong.

You're welcome guys 😊👍


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