General Thoughts: Chemistry (5 Viewers)

[born2prevail]

Lol this year's state rank will probably be like 99-100% right?

 

[SilentWaters]

For Q.13 MC:

B is correct. There are 2 ways to justify this:

(1) [Paraphrasing the sample answers for Q23 of 2009] Halving the volume will increase the concentration of all reagents proportionally, according to the stoichiometry of the reaction. The left hand side (nitrogen and hydrogen) constitute a greater number of gas moles, and hence proportionally they are more affected by the increase. The system (by LCP) moves to decrease their concentration to compensate for this, resulting in an increase in concentration of ammonia on the product side.

(2) We know that decreasing volume increases the partial pressures of the gases. By LCP, the system shifts to favour the side with fewer gas moles. Hence the concentration of ammonia increases slightly.

 

[GOsie]

Band 6 cutoff this year?

 

[someslovak]

I reckon raw 95. Studied so much for soaps and we got the seven marker on it in industrial!!

 

[the_lebtalian]

Exam wasn't as bad as I was expecting, although probably lose heaps of marks cause of bitchy hsc markers

 

[GOsie]

I reckon raw 95. Studied so much for soaps and we got the seven marker on it in industrial!!

I'm hoping you're not replying to my question :/

 

[emilios]

Wait what? that CO2 purity q was 80%? I didnt get that :/ :/ :/

 

[born2prevail]

i Thought it was once the overall concentrations have increased, the ratio needs to be re-achieved, so the H and N increase slightly, and the ammonia decreases slightly, because the overall concentration was increased at a ratio of 1:1

 

[SilentWaters]

Anyone with the paper, feel free to post up your MC answers!

 

[GOsie]

Wait what? that CO2 purity q was 80%? I didnt get that :/ :/ :/

neither. I got like 20% or so. Don't remember the exact number

 

[iStudent]

purity q i got 80
if was mass c/Total mass right?

 

[born2prevail]

It was 80% u do the moles found in part (i) - the moles found in the titration with HCl, divide that by 2, and multiply by molecular mass of CO2, then divide that by original amount.

 

[iStudent]

80 also makes more sense intuitively than 20... (lol 20% carbon in dry ice?)

 

[SilentWaters]

i Thought it was once the overall concentrations have increased, the ratio needs to be re-achieved, so the H and N increase slightly, and the ammonia decreases slightly, because the overall concentration was increased at a ratio of 1:1

Don't know what you mean by 1:1, but this is a comparison of gas moles between the cumulative moles of nitrogen and hydrogen, with that of ammonia (4:2). The increase, therefore, affects the reactant side more than the product side. Compensation for this must come by a decrease on the left and increase on the right.

Look at the 2009 question I cited - that MC question was simply a reverse of what happened (i.e. volume decreases rather than increases in this one).

 

[ushnakhalid]

easy exam, industrial was wonderful as well. Expecting the marking to be super tough. Ps got 80% for the purity question.

 

[QZP]

Yeah easy exam because of generic questions.

 

[3429769]

For the purity question i left the answer as 79.73%, because i used the number of moles to about 9 digits.

Do you reckon i'll get 4 or will the infamous BOS markers take a mark off?

 

[shved]

What did ship rekt people write for the last question of shipwrecks?

I wrote how you're supposed to slowly increase the voltage in an electrolytic cell and some other crap

 

[enigma_1]

I wrote how you're supposed to slowly increase the voltage in an electrolytic cell and some other crap

dafuq

why is this information not available in textbooks..

 

[photastic]

For the purity question i left the answer as 79.73%, because i used the number of moles to about 9 digits.

Do you reckon i'll get 4 or will the infamous BOS markers take a mark off?

Yes cos the question gave u 2 sig figs, hence the answer should also be in 2 sig figs which was 80%