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General Thoughts: Chemistry (1 Viewer)

dan964

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relatively good
I loved that 7 marker on ethanol
I reckon I got 89-99 (probs 92-94)
screwed up MC got 19/20 probs. (Got Q1 can you believe it wrong?)

Comment for correction:

1. D - it is not B (which I put stupidly) and the rest are clearly wrong because ozone is not even in those layers
2. A - lowest locant must be on "bromo" and then "fluoro" not the other way around.
3. B - by elimination, Arrhenius was hydrogen ions, Davy was hydrogen and Lavoisier was oxygen
4. C - by elimination, A is clearly wrong, B is not cracking it is polymerisation, D is not breaking up larger hydrocarbons
5. C - by elimination, A & B are both wrong as there is not double bond in the reactant, D is wrong as well
6. B - (not exactly sure, please confirm), because all values are the lowest except for dissolved oxygen which is good. D is wrong
7. C - by elimination, D is wrong because ammonia is pink in phenolphthalein, and A & B are wrong because they are not yellow in methyl red.
8. B - make sure to note temperature decrease, ph goes up, therefore [H+] goes down. D is wrong because think it about the chemistry of ionisation.
9. A - because Y can't be an isomer with any of the other options eliminating B, C and D
10. C - because either H2O and OH- are paired or HOCl and OCl- are paired. C is the later the rest are wrong.
11. C (pretty certain) - B & D are obviously coordinate covalent bonds. A is too. C is not, because the dipoles cancel.
edit: 11 A. is confirmed as correct

12. C - A & B are wrong, pH is a logarithmic scale, and also D is wrong it is [H+] you are after.
13. A (not exactly sure) - C & D are wrong because if the volume is halved, pressure goes up, so ammonia increases. B is not quite right, because it would shift back towards a certain ratio. Could be B.

edit: 13 B. is confirmed as correct

14. D - use the formula makesure to include the negative
15. D - convert each to moles, the most moles of substance is the biggest i.e. D. All the reactions are 1:1.
16. B - check the oxidation numbers for A & D it goes up, for C it doesn't change, therefore B is correct
17. A - chromate is reduced, and SO2 is oxidised therefore A. Not B because the oxidiation potential of SO2 is not 0.16 but -0.16
18. D - compare the structures, A to C are all inconsistent with the diagram given above.
19. B - calculation
20. D - can't be A or C because think Haber process exothermic reaction, lower temperature better. as pressure goes up, shifts to the right, i.e. side with less molecules, therefore B is wrong.


#sydneytrains train Airport Line (13:30), 30 minutes late***
actually 20 minutes but by connecting train was only 10 minutes late (meaning I missed it)
 
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bhatman

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oh crap I just realised I wrote the ionic equation to show precipitates. Omg am I screwed? :(
that's perfectly fine if it's something like Ba2+ + SO42- --> BaSO4
if not, do you mean multiple reactions involving the transfer of electrons?
Because I really don't know if they'll mark you down for writing more equations, judging by comments on this thread
 

enigma_1

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that's perfectly fine if it's something like Ba2+ + SO42- --> BaSO4
if not, do you mean multiple reactions involving the transfer of electrons?
Because I really don't know if they'll mark you down for writing more equations, judging by comments on this thread
Yeah I used that exact equation, and one only. I should have just done the whole one :(

Hopefully they don't take off a mark for that.
 

bhatman

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Yeah I used that exact equation, and one only. I should have just done the whole one :(

Hopefully they don't take off a mark for that.
They really can't because you're showing the reacting species anyways. The NO3- ion just ends up as a spectator in solution anyways
 

photastic

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It says what happens when temperature DECREASES, not increases. When temperature DECREASES, pH increases, this means that the acid is becoming less acidic. The equilibrium would be set up as shown:
HA <=> H+ + A-
If pH increases, that means equilibrium is SHIFTING TO THE LEFT.
If that's the case, that means the acid is coming LESS ionised and H+ concentration must be decreasing.
Fkkkkkkkk! I read it as increase why why! Why didnt I read
 

iStudent

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Exam choice 2009 q21 in case any of you guys are wondering where bostes basically STOLE one of their questions from
 

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