# A2 and AS Chemistry OCR Practical Exam

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#1
Just wondering if anyone ele is doing it. The AS one is pretty straight forward but the A2 one is a little more complicated! It's to design the decompsition of Hydrogen peroxide, to find the order of reaction and if surface area of a catalyst changes the rate. Most of the good catalysts are powders which means.......loads of calculations!........arghhhh
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16 years ago
#2
Im doing this 1 also...

- Plan an experiment that would enable you to find out weather or not the rate of decomposition depends on the surface area of the solid catalyst used.

- Plan another experiment by which you could determine the order of reaction for this decomposition with respect to hydrogen peroxide.

Any1 any suggestions for stuff to include?
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16 years ago
#3
yup i got to do it 2!!! argh!!!
u no for the second part, bout the order of reaction we can keep the catalyst surface area constant and dilute the solution. got ne ideas on how to dilute the thing to weaker concentrations??
the stuff is apparently 10 volume which means...

1cm3 of hydrogen peroxide will give 10cm3 of oxygen gas under decompostion.

so wed use 10cm3 to get 100cm3 of gas as 10cm3 wud happen 2 fast.

so if the solution was diluted to 5volume 1cm3 wud give 5cm3 of gas...

but each time we wana collect 100cm3 to keep this variable constant, so wud i add 10cm3 of water to the original 10 volume solution, making it 5volume?? then this 20cm3 of 5volume solution wud give 100cm3 of gas???

am i on the right lines?? any ideas wud be greatly appreciated??
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16 years ago
#4
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16 years ago
#5
HELLO??? person in need of great help with the A2 chemistry, any1 with any ideas??
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16 years ago
#6
what catalyst you guys using?
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16 years ago
#7
i did my chemistry practical thie weekend, the surface area part is quite easy, changing the surface area is the same as the amount u use. so to change the surface area of the catalyst all u need to do is change the amount of it u use. so in one of the investigation su could u could use 0.1 g and 0.2g in the other.
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16 years ago
#8
Adding ethanol to the ethanoic acid is not a positive chemical test accepted by the exam board. I have a test for the nitric acid, but does anyone know another way to test for the ethanoic acid? post a message if so!

thanks,

K
xxx
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16 years ago
#9
A +ve test for an -OH group (alcohols & carboxylic acids) is to add PCl5(s), which gives steamy white fumes of HCl(g). Problem is, this reaction is not in the AS spec. I will use it anyway.

Can anyone assist me with my method? As we're testing unknown solutions, I proposed to test a small sample of each of the 5 solutions (in a test-tube) with each test I intend to propose, e.g. add AgNO3 to each tube, shake, leave to stand and make obs; add dilute NH3 to those which reveal a white and cream ppte, shake, and leave to stand. AgCl will be sol in dil. NH3, whereas AgBr will only dissolve in conc NH3. Am I on the right lines?

The remaining tubes that didn't show +ve result to the halide ions test, will be tested for the presence of Ca(OH)2, HNO3 & CH3COOH. Again, if the brown ring test is confirmed by one of the 3 solns, then a credible inference can be made, etc.
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16 years ago
#10
hot reflux with conc. H2SO4
ethanoic acid + ethanol ----------------------------------> ester+ water

the ester is Ethy Ethanoate

you can smell this ester distinctively!!!
thus a positive test!!!!
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16 years ago
#11
http://www.studyzones.com/funzone/re...B0D049C8DF.htm

Check out the above site. The questions are answered by teachers.
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16 years ago
#12
Hey. A bit late for anyone involved. But i had a peek at the lab after they set up today and its almost certainly a titration where we make up one of the solutions because there is a volumetric flask and mass balance. Good luck everyone!
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16 years ago
#13
PLZ CAN COMEONE HELP ME ON THE TITRATION PART OF THE CHEM PLANNING. I HAVENT GOT A CLUE ON IT
THANX
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16 years ago
#14
i hope its an easy one for a change,anyone else worried bout the practical tmorrow? i swear i cant do them,i try but i always get them wrong.
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16 years ago
#15
Im guessing u are talking about the AS one thats 2morrow, cos ive got the A2 one next week i think! Gotta hand in this plan 2 morrow tho.
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#16
You guys think it was ok! the AS one was alright, Titrations are too easy. If you all looked at last years exam paper nuff of the questions and calculations where the same. The A2 one this wednesday and I'm finaly finishing my dahm plan! bout time!
*E*
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16 years ago
#17
[QUOTE]Originally posted by Unregistered
PLZ CAN COMEONE HELP ME ON THE TITRATION PART OF THE CHEM PLANNING. I HAVENT GOT A CLUE ON IT
THANX
[/i dont have a clue either]
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