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WJEC Chemistry Practical
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GulfamChoudhary
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#1
Hi there does any1 know what the practical is about. Our teacher isnt telling us whilst my other subject teachers have. Thx in advance 
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GulfamChoudhary
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nathanwjec
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#3
(Original post by GulfamChoudhary)
Hi there does any1 know what the practical is about. Our teacher isnt telling us whilst my other subject teachers have. Thx in advance
Hi there does any1 know what the practical is about. Our teacher isnt telling us whilst my other subject teachers have. Thx in advance
Rather than relying on knowing what the practical is, have a think what it could be:
Titration- double, back, pH or redox
Qualitative analysis- chemical reagent and tests
Determining the order of a reaction
Determining enthalpy change
Electrochemistry
Determination of equilibrium constant
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omacmano98
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#4
The one tomorrow (wednesday) is two titrations, acid base, phenolphthalein indicator. You will then have to identify the compound. Also, learn the tests for halide ions, aldehydes and ketones.
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nathanwjec
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#5
How did everybody find that? I got butanoic acid for the acid we were given, positive dichromate test, positive iodoform test (I made this up as I assumed it was supposed to be positive), negative halide ion test.
When we had to suggest a structure I put CH3CH(OH)CH2COOH
When we had to suggest a structure I put CH3CH(OH)CH2COOH
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jaisuf
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#6
(Original post by nathanwjec)
How did everybody find that? I got butanoic acid for the acid we were given, positive dichromate test, positive iodoform test (I made this up as I assumed it was supposed to be positive), negative halide ion test.
When we had to suggest a structure I put CH3CH(OH)CH2COOH
How did everybody find that? I got butanoic acid for the acid we were given, positive dichromate test, positive iodoform test (I made this up as I assumed it was supposed to be positive), negative halide ion test.
When we had to suggest a structure I put CH3CH(OH)CH2COOH
Only difference for mine was OH was on the end - since I had negative iodoform test
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jaisuf
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#7
How many marks do you reckon I’d lose for getting the wrong result for iodoform, and hence a slightly wrong structure? (OH one to the left of where it should be). I’d hope not many personally aha
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cowseatmilk
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cowseatmilk
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#9
(Original post by jaisuf)
How many marks do you reckon I’d lose for getting the wrong result for iodoform, and hence a slightly wrong structure? (OH one to the left of where it should be). I’d hope not many personally aha
How many marks do you reckon I’d lose for getting the wrong result for iodoform, and hence a slightly wrong structure? (OH one to the left of where it should be). I’d hope not many personally aha
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jaisuf
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#10
(Original post by cowseatmilk)
I'd imagine 2. One for the incorrect observation and 1 for the incorrect structure
I'd imagine 2. One for the incorrect observation and 1 for the incorrect structure
I’m not a fan of iodoform tests tbh, I did mine literally 3 times and it was completely clear every time. Also technicians realised one of the water baths was off for most of the exam, so my original iodoform would have been wrong anyway (still got clear afterwards tho)
Grim
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cowseatmilk
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#11
(Original post by jaisuf)
Yeah, hopefully no more than that. Although I do wonder if it’s possible for my structure to lose no marks, since it’s accurate to my observation.
I’m not a fan of iodoform tests tbh, I did mine literally 3 times and it was completely clear every time. Also technicians realised one of the water baths was off for most of the exam, so my original iodoform would have been wrong anyway (still got clear afterwards tho)
Grim
Yeah, hopefully no more than that. Although I do wonder if it’s possible for my structure to lose no marks, since it’s accurate to my observation.
I’m not a fan of iodoform tests tbh, I did mine literally 3 times and it was completely clear every time. Also technicians realised one of the water baths was off for most of the exam, so my original iodoform would have been wrong anyway (still got clear afterwards tho)
Grim
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nathanwjec
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#12
(Original post by jaisuf)
How many marks do you reckon I’d lose for getting the wrong result for iodoform, and hence a slightly wrong structure? (OH one to the left of where it should be). I’d hope not many personally aha
How many marks do you reckon I’d lose for getting the wrong result for iodoform, and hence a slightly wrong structure? (OH one to the left of where it should be). I’d hope not many personally aha
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Akire
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#13
How many marks do you think I will lose if my results are not concordant to that of the teacher
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nathanwjec
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#14
(Original post by Akire)
How many marks do you think I will lose if my results are not concordant to that of the teacher
How many marks do you think I will lose if my results are not concordant to that of the teacher
Generally this is how the marks are given, based on how close your value was to your teachers value:
Within 0.2cm3 - 5 marks
0.3cm3 - 4 marks
0.4cm3 - 3 marks
0.5cm3 - 2 marks
0.6cm3 - 1 mark
So, if you didn’t get within 0.6cm3 then you would get 0 for that titration
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science234
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jaisuf
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#16
(Original post by nathanwjec)
I can’t remember exactly how many marks the titration readings are worth. I’m pretty sure it’s 5 marks for each titration.
Generally this is how the marks are given, based on how close your value was to your teachers value:
Within 0.2cm3 - 5 marks
0.3cm3 - 4 marks
0.4cm3 - 3 marks
0.5cm3 - 2 marks
0.6cm3 - 1 mark
So, if you didn’t get within 0.6cm3 then you would get 0 for that titration
I can’t remember exactly how many marks the titration readings are worth. I’m pretty sure it’s 5 marks for each titration.
Generally this is how the marks are given, based on how close your value was to your teachers value:
Within 0.2cm3 - 5 marks
0.3cm3 - 4 marks
0.4cm3 - 3 marks
0.5cm3 - 2 marks
0.6cm3 - 1 mark
So, if you didn’t get within 0.6cm3 then you would get 0 for that titration
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YellowCurryNinja
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#17
(Original post by nathanwjec)
How did everybody find that? I got butanoic acid for the acid we were given, positive dichromate test, positive iodoform test (I made this up as I assumed it was supposed to be positive), negative halide ion test.
When we had to suggest a structure I put CH3CH(OH)CH2COOH
How did everybody find that? I got butanoic acid for the acid we were given, positive dichromate test, positive iodoform test (I made this up as I assumed it was supposed to be positive), negative halide ion test.
When we had to suggest a structure I put CH3CH(OH)CH2COOH
I had the same as you for the tests, but the dichromate in our school messed up so it went from orange to blue lmao.
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nathanwjec
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#18
(Original post by YellowCurryNinja)
I had Ethanoic Acid for the acid given because I messed up my calculation (did the method right, but inserted the volume of NaOH instead of Volume of acid, because I'm an idiot). My Mr was 59.01 as a result of that (rounded to 60 for Ethanoic Acid). I had the same as you for the suggested structure, but it was HEAVILY disputed between people that it was either CH3CH(OH)CH2COOH or CH3CH(OH)COOH (5 of the smartest people in our year who had straight A's last year, had the latter value, whereas a lot of others had the former).
I had the same as you for the tests, but the dichromate in our school messed up so it went from orange to blue lmao.
I had Ethanoic Acid for the acid given because I messed up my calculation (did the method right, but inserted the volume of NaOH instead of Volume of acid, because I'm an idiot). My Mr was 59.01 as a result of that (rounded to 60 for Ethanoic Acid). I had the same as you for the suggested structure, but it was HEAVILY disputed between people that it was either CH3CH(OH)CH2COOH or CH3CH(OH)COOH (5 of the smartest people in our year who had straight A's last year, had the latter value, whereas a lot of others had the former).
I had the same as you for the tests, but the dichromate in our school messed up so it went from orange to blue lmao.
As for the structure: as long as your structure matches up with your data you will be fine!
Also if you looked at the nmr spectrum, it couldn’t have been the 3 carbon compound, it had 4 or 5 readings can’t remember; 4/5 hydrogen environments and in the stem it stated it was only PART of the spectrum
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jaisuf
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nathanwjec
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#20
(Original post by jaisuf)
Good luck to everyone for tomorrow!
Good luck to everyone for tomorrow!
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