General thoughts: HSC chemistry 2015 (5 Viewers)

[Librah]

the K question wasnt even hard lol. Just use an ICE table and you are sweet. I'm glad they asked a K question as it is by far the most routine and easiest part of industrial chemistry.

Everyone seems to be getting different answers for it lol

 

[el_manu]

Marking criteria changes over time

I think they'd be looking for you to be specific with the type of polystyrene and polyethylene so I talked about LDPE, HDPE, crystal polystyrene and expanded polystyrene just to be safe

same. I also drew the branching of LDPE and the dense HDPE as well.

 

[nerdz1]

D

Can somebody confirm this? I personally do not think it is D because despite the hydroxyl groups reacting in the middle correctly, if you have 2 of these units placed side by side, you would have a C - O - O - C bond which should't be so right?

I picked B because of this.

 

[rohanbalani]

Again if anyone has it, the K question from Industrial that everyone's complaining about please.

Found it on Facebook.

 

[apurba]

Can somebody confirm this? I personally do not think it is D because despite the hydroxyl groups reacting in the middle correctly, if you have 2 of these units placed side by side, you would have a C - O - O - C bond which should't be so right?

I picked B because of this.

A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their broad range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life.

Note that it says "repeated subunits."

There are no repeated units for option B, and hence the answer must be D.

 

[myinnermonkey]

lol, do you know what you are saying? When they say with reference to the graph, that means you only speak about temperatures and pressures. You wouldn't speak about ratio of reactants or concentrations of contaminants as it wasn't mentioned in the graph. 3 marks for temperature and 3 marks for pressure is enough, no need to speak about anything else unless if it relates to temperature (for example excessively high temperatures melt catalyst) and pressure (excessively high pressures are hard to maintain, dangerous, etc.)

Imo, 3 marks for each is like giving away easy marks, but I guess it depends on their marking criteria this year. But for an exam like that, I feel like they wouldn't be as lenient bc then it doesn't really distinguish the top students. Idk, I might be wrong and you could be right, but for sciences I think giving more information is better bc the criteria can be really specific but in this case talking about the catalyst does actually relate to temperature..

 

[Librah]

Can somebody confirm this? I personally do not think it is D because despite the hydroxyl groups reacting in the middle correctly, if you have 2 of these units placed side by side, you would have a C - O - O - C bond which should't be so right?

I picked B because of this.

Anyway though, it's not B, because by MC common sense

 

[malcolm21]

The question didn't specifically ask for temperature and pressure; they asked for conditions with reference to the graph. This means that you talk about all the conditions, and talk about the graph in relate to temp and pressure. To talk about temp conditions, you have to say that haber process uses moderate temperatures of 400-450 degrees, however the graph shows that maximum yield is obtained from 500atm and 200 degrees. This low temperature would however mean that the reaction rate is very slow so production isn't efficient, thus that's why 400 degrees is usually used. To further compensate for the slow reaction rate, magnetite catalyst is used. For a six mark question, I don't think talking only about temperature and pressure is enough tbh

do you think i can get full marks if i forgot the name of the catalyst lol. i wrote about temperature cant be too high or the catalyst will get damaged but never named it

 

[myinnermonkey]

do you think i can get full marks if i forgot the name of the catalyst lol. i wrote about temperature cant be too high or the catalyst will get damaged but never named it

I don't think it's necessary to actually name the catalyst as long as you acknowledged it

 

[Librah]

View attachment 32590

Found it on Facebook.

I got 10.6. And yeah, it's just your typical K calculation... I think it might want 11 (2 s.f)

 

[TQuadded]

do you think i can get full marks if i forgot the name of the catalyst lol. i wrote about temperature cant be too high or the catalyst will get damaged but never named it

You want to be very specific and use scientific language when answering Science questions.

 

[InteGrand]

Lol as expected, equilibrium constant question was standard (they never really ask you harder ones).

 

[kawaiipotato]

Can somebody confirm this? I personally do not think it is D because despite the hydroxyl groups reacting in the middle correctly, if you have 2 of these units placed side by side, you would have a C - O - O - C bond which should't be so right?

I picked B because of this.

That's what i thought but everyone is saying its D.

 

[monopoly73]

the past HSC question didnt say include a diagram either! i remember VIVIDLY being angry at the criteria since it didnt specify, but I learnt my lesson and drew a diagram of each one today.

I swear on my life brah

no he is right because my chem teacher is the head hsc marker for chemistry board of studies and she said that you needed a diagram

 

[malcolm21]

no he is right because my chem teacher is the head hsc marker for chemistry board of studies and she said that you needed a diagram

wtf ur not allowed to teach if you have impact on the tests conflict of interest reporting ur teacher to bostes

 

[nerdz1]

A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their broad range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life.

Note that it says "repeated subunits."

There are no repeated units for option B, and hence the answer must be D.

By IUPAC convention, the brackets imply the if you essentially place the unit side by side, then it should work out to be the actual polymer. However, with D, this does not work. See: https://en.wikipedia.org/wiki/Repeat_unit and their example with condensation polymers. If you place the unit side by side, you get a C - O - C bond which works out correctly.

 

[Librah]

That's what i thought but everyone is saying its D.

I think it may be B, since D is actually wrong, but HSC never throw curveballs so i'm skeptical.

 

[nerdz1]

Can somebody who got 10.6 for the K question show me how they did it? Thanks

 

[JAMLO]

Can someone please upload the paper pllzzz

 

[synx]

Btw does anyone have any idea of when sample solutions may be posted up? thanks