OCR A-level Chemistry A H432 [2018 Exam Discussion]

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Nadiya5
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#1
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#1
Hi! Figured I would make this one as well, seeing as no one else has so far ~





Upcoming Chemistry Exam Dates:




  • Tuesday 5th June 2018 - (Paper 1) H432/01: Periodic Table, Elements and Physical Chemistry

Time: Afternoon
Duration: 2hrs 15mins

  • Tuesday 12th June 2018 - (Paper 2) H432/02: Synthesis and Analytical Techniques

Time: Afternoon
Duration: 2hrs 15mins

  • Wednesday 20th June 2018 - (Paper 3) H432/03: Unified Chemistry

Time: Morning
Duration: 1hr 30mins





Good luck guys !!!



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786hasan123
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#2
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#2
Anyone got any predictions for Paper 1. I think Born Haber will come up seen as it didn't come up on any of the 2017 papers.
Thanks
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hihiih
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#3
bump
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aqsahawan
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#4
I have a hunch that standard solutions and more complex buffer questions will come up , anyone have weird calculation questions they want to share ?
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briefcase
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how do you do enthalpy of solution and hydration and etc
(Original post by aqsahawan)
I have a hunch that standard solutions and more complex buffer questions will come up , anyone have weird calculation questions they want to share ?
i secknd this. any exampls
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FluuidKarma
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(Original post by briefcase)
how do you do enthalpy of solution and hydration and etc


i secknd this. any exampls

to calculate enthalpy of hydration/solution

hess's law mate

enthalpy of solution=enthalpy of hydration-lattice enthalpy

this is because when you dissolve an ionic solute:
1) the ionic lattice is broken to form gaseous ions (OPPOSITE OF LATTICE ENTHALPY)
2) the gaseous ions form bonds with water molecules, dissolving them (ENTHALPY OF HYDRATION)

this is reflected in the equation above.
in the exam you just have to plug in given values into that equation to find the unknown value.

if you're still stuck read this: https://www.chemguide.co.uk/physical.../solution.html

example of a tricky acid calculation

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i personally found this question really hard (red highlighted one)
the solution is:
Spoiler:
Show

you have to rearrange the Ka=[H+][A-]/[HA] equation, piece of cake after that! sneaky though.


standard solution example

and yeah for standard solutions there's this question from the set 2 paper
Attachment 752360752364

that's as difficult as i imagine it getting tbh, mark scheme is on side if you want to see how that's marked. it is strictly a practical based thing fyi.

as always, go through the spec online. chem is kinda blessed bc it's small AND they will never go off spec. literally everything on the paper last year could be found on the spec. strongly recommend going over the maths section to make sure there's nothing you miss there.

also, remember colorimetry! you use the opposite colour for the filter to the reactant solution so you measure the absorbed light.
to find concentration:
calibrate colorimeter create standard solutions and measure absorbance of standard solutions to obtain reference values, plot on a graph with concentration (x) against absorbance (y) to create calibration curve. measure absorbance of unknown sol., compare to calibration curve to find out concentration.

good luck everyone! X
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candifloss
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#7
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#7
thank you!!
ngl i didn't clock that this was an afternoon exam lool

GOOD LUCK EVERYONE
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mansnothot
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#8
i made a thread about a chem question could anyone help?
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Lia22
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#9
Do we need to know the indicator names?
And also...
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Where is say 'explanation of...'
Is that basically the definition we need to learn?
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username2312801
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#10
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#10
Hoping its similar to last years paper and not too hard
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ZAYN zain
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#11
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#11
What is the answer for the acid qn
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mansnothot
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#12
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#12
what does the ratio of [HA]:[A-] tell you about ph
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anonymous0018
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#13
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#13
someone please help me with this question
The half-life for the first order reaction is 688 hrs at 1000°C CS2 (g) --> CS (g) + S (g)
a) Calculate the specific rate constant value and units.
b) Calculate the amount of a 3.0 g sample of CS2 remaining after 48 hours.

i got the answer for part a (0.00100748) but i dont understand part b
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hihiih
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#14
Gone through the revision guide and new spec papers but i feel like i wouldnt know how to do a big mark question on setting up practical experiment, anyone got any recommendations for ones i should learn that or more likely to come up?
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mansnothot
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(Original post by hihiih)
Gone through the revision guide and new spec papers but i feel like i wouldnt know how to do a big mark question on setting up practical experiment, anyone got any recommendations for ones i should learn that or more likely to come up?
what type of practicals?
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mansnothot
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#16
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(Original post by anonymous0018)
someone please help me with this question
The half-life for the first order reaction is 688 hrs at 1000°C CS2 (g) --> CS (g) + S (g)
a) Calculate the specific rate constant value and units.
b) Calculate the amount of a 3.0 g sample of CS2 remaining after 48 hours.

i got the answer for part a (0.00100748) but i dont understand part b
how did u get part a?
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anonymous0018
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#17
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#17
by using the half life equation
k= ln(2)/half life
so ln(2)/688
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hihiih
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#18
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#18
(Original post by mansnothot)
what type of practicals?
for the physical exam tomorrow just if you think there are any specific ones that we may be asked to set up, i could explain how to set up titration and electrochemical cells for example but im not sure what else they might ask. not sure if ive explained that well?!
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mansnothot
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(Original post by hihiih)
for the physical exam tomorrow just if you think there are any specific ones that we may be asked to set up, i could explain how to set up titration and electrochemical cells for example but im not sure what else they might ask. not sure if ive explained that well?!
i think thats all i dont even know any tbh . could u explain how to set up titration? thanks
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anonymous0018
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#20
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#20
(Original post by hihiih)
you know that after 688 hours the product left would be 1.5g so wouldnt it just be 3 - (48/688 x 1.5)?
wow i didnt think about it like that
thanks
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