VCAA Chemistry Examination - AN Official Solutions (Draft 1)

[thushan]

Here you go. If there's an error just post here.

[Stick]

Thanks!

[Kayte]

You forgot Question 4d

[Stick]

I have a feeling 6d is incorrect. Combustion reactions are exothermic and so the energy of the products is lower than that of the reactants. Probably just a brief mental blank.

[Patches]

edit: saw your explanation in the other thread
Out of curiosity, for Q5 part D, how do the amounts of ethanoic acid and ethanoate ions become equal? Surely if you've added half the amount of NaOH, half of the acid is going to be neutralised as ethanoate, and a little bit of the remaining acid will also be ionised so there's more than half of the acid present as ethanoate ions? Or are we meant to assume they're equal even though they're not?

Also Q10 bii is balanced wrong - the number of O2 should be 80.

[Stick]

Also, I think the combustion equation in 8ai is incorrect.

EDIT: I think the combustion equation in 10bii is also incorrect. :S

[teletubbies_95]

OMG lost like 6 marks !

[achre]

For 6b, would I lose the mark for writing ethene as CH2CH2 instead of CH2=CH2?

[thushan]

Top of page 6 should be in Litres


And I'm a bit worried now lol

Nah its mL - density is given in g mL^-1.

And yeah rawr - Q4d - Biomass is derived from recently living plant material, whereas fossil fuels is derived from plant material that has been dead for a long time, whose stores are only very slowly being replenished.

And Stick you're right - will fix. Man I'm so tired.

[Stick]

OMG lost like 6 marks !

I think I lost the same amount. Don't be sad - 114/120 is a great score!

[Stick]

And Stick you're right - will fix. Man I'm so tired.

Yeah, it's like your brain... combusted.

[thushan]

Ha. Ha. Fixed btw - new doc's up.

[charmanderp]

Interested to hear your reasoning for question 13 Thush.

Also for 30, I'd have thought the answer would be D, not C. Given that all three solutions are aqueous, there shouldn't be any metal deposited onto the electrode in the solution containing K+ because H2O would be reduced in preference to K+ for an infinitely long amount of time, producing no metal (K+(aq) is never reduced to K(s))

[thushan]

Interested to hear your reasoning for question 13 Thush.

Also for 30, I'd have thought the answer would be D, not C. Given that all three solutions are aqueous, there shouldn't be any metal deposited onto the electrode in the solution containing K+ because H2O would be reduced in preference to K+ for an infinitely long amount of time, producing no metal.

Frick this.

[Stick]

Interested to hear your reasoning for question 13 Thush.

Yes, please do explain, because I'm still not following the common solution of B. :S