• Congratulations to the Class of 2024 on your results!
    Let us know how you went here
    Got a question about your uni preferences? Ask us here

General Thoughts: Chemistry (1 Viewer)

dan964

what
Joined
Jun 3, 2014
Messages
3,480
Location
South of here
Gender
Male
HSC
2014
Uni Grad
2019
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)
 
Last edited:

bhatman

Member
Joined
Jun 10, 2014
Messages
63
Gender
Male
HSC
2014
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

~~~~ Miss Cricket ~~~~
Joined
Feb 27, 2013
Messages
4,281
Location
Lords
Gender
Female
HSC
2014
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

Member
Joined
Jun 10, 2014
Messages
63
Gender
Male
HSC
2014
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

Well-Known Member
Joined
Feb 11, 2013
Messages
1,848
Gender
Male
HSC
2014
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

Well-Known Member
Joined
Mar 9, 2013
Messages
1,158
Gender
Male
HSC
2014
Exam choice 2009 q21 in case any of you guys are wondering where bostes basically STOLE one of their questions from
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top