Originally posted by Thefire521:What i did was i completed half of q3. But saw the long deduction question so i just continued with q4 and q5 they were finished in arnd 30 minutes. Why did you not move on to try the rest?
I had around fifteen minutes left to attempt Q4 and give up on Q3 . But I thought I might try to queeze one to two marks out of Q3 because I've already secured ten marks there. I thought I barely had time to secure equivalent marks for Q4. That's why. But i made up for the marks with other Questions thankfully.
Is the question about voltage decrease due to no salt bridge?
Originally posted by Thefire521:Did you guys remember to distill away the alcohol after forming ur r-cl?
Hi, are you referring to Q5? Didn't attempt it
Originally posted by lalalaboi998:Is the question about voltage decrease due to no salt bridge?
It's about non-standard molarities as reaction progresses, [Zn2+] increasing, [Cu2+] decreasing, Le Chatelier's principle, less positive reduction potential for Cu2+/Cu, less positive oxidation potential for Zn/Zn2+, hence less positive Cell potential.
Originally posted by lalalaboi998:Is the question about voltage decrease due to no salt bridge?
No.
Originally posted by UltimaOnline:
No.It's about non-standard molarities as reaction progresses, [Zn2+] increasing, [Cu2+] decreasing, Le Chatelier's principle, less positive reduction potential for Cu2+/Cu, less positive oxidation potential for Zn/Zn2+, hence less positive Cell potential.
Agreed. Was thinking this was the only point they actually tested equilbrium shifts ( i think) in the entire 2 papers.
Luckily they didn't test buffers, pka graphs.
Oh thnx thnx
Originally posted by Thomas00:Luckily they didn't test buffers, pka graphs.
They totally ignored kinetics as well, which is peculiar.
Many of the questions were just simple write combustion rxns, write free radical rxns... compare reactivities, you just gotta follow instructions.. talk about clf3... standard q
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Originally posted by DemonicTable:Just curious, for the calculation of bond energy in 2(b), I carelessly drew the arrow for bond energy in the wrong direction hence obtaining negative answer. Will I be penalised fully in both parts of 2(b)?
Your part b i answer would have been wrong. part b ii was on entropy so its unrelated.
Originally posted by DemonicTable:Just curious, for the calculation of bond energy in 2(b), I carelessly drew the arrow for bond energy in the wrong direction hence obtaining negative answer. Will I be penalised fully in both parts of 2(b)?
Originally posted by Thefire521:They totally ignored kinetics as well, which is peculiar.
Many of the questions were just simple write combustion rxns, write free radical rxns... compare reactivities, you just gotta follow instructions.. talk about clf3... standard q
Yup. Also not much protein chemistry although last year i think.
Originally posted by ArJoe:Hi for the last question, it is acidified kmno4, dry pcl5
then the second one is liquid bromine, excess concentrated nh3, heat in a sealed tube?And for qn 3 the deduction, is it geometrical isomer and 4 isomers?
Last Q5 should be oxidative cleavage, PCL5 s RT for steps 1 and 2
but your second one should not be using Br2 because you will get disub
You should be using HCL(g) or similar
Originally posted by Thefire521:Last Q5 should be oxidative cleavage, PCL5s RT for steps 1 and 2
but your second one should not be using Br2 because you will get disub
Hi what is the answer for the energy cycle qn? Just wanna see if i got it correct
Originally posted by ArJoe:Hi for the last question, it is acidified kmno4, dry pcl5
then the second one is liquid bromine, excess concentrated nh3, heat in a sealed tube?And for qn 3 the deduction, is it geometrical isomer and 4 isomers?
Originally posted by Thefire521:Your part b i answer would have been wrong. part b ii was on entropy so its unrelated.
Q3. Both optical isomerism / enantiomerism, *and* geometrical isomerism / cis-trans / E-Z isomerism. Hence total stereoisomers = 2^2 = 4.
Originally posted by Jlptj:Hi what is the answer for the energy cycle qn? Just wanna see if i got it correct
For energy cycle
1). Did you times the enthalpy change of formation by 2 if you used the equation given
2). Did you times the vaporisation enthalpy by 2 if you used the equation given
3). Was your bond energy arrow in the correct direction (so you get a positive value at the end)-using a negative arrow means you dont understand the definition of bond energy-of course lose marks, but they will give you marks for knowing how to apply your cycle to your final answer
4). Did you include the bond breaking energies for Br2 and 3F2 from the data booklet?
Originally posted by Thefire521:Q3 for the last part people around me were telling me its structural isomers!
Originally posted by ArJoe:
But do i get marks for writing correct reagent in step 4?
Of course the 7 marks are allocated for each reagent and each intermediate drawn correctly. So if you get 3/7 right then you get 3/7..
Ultima, which questions u find more time consuming?
Is the percentage by mass 44%? And for the cell diagram is it O2 on one side and methane gas on the other?