HSC 2012-2015 Chemistry Marathon (archive) (2 Viewers)

[bleakarcher]

re: HSC Chemistry Marathon Archive

1. Alkanes & alkenes are non-polar (symmetrical structure). Intermolecular forces between alkane & alkene molecules are only dispersion forces. As there are more electrons with compounds having more electrons, there are stronger temporary induced dipoles so there'll be stronger dispersion forces.
2. Be more specific - intermolecular bonds!
3. State that melting point & boiling point are directly proportional to the degree/strength of intermolecular bonding between the molecules.

I thought I never heard of dipoles and alkanes(/enes).

 

[Magical Kebab]

re: HSC Chemistry Marathon Archive

I thought I never heard of dipoles and alkanes(/enes).

My bad I completely forgot.

Haya's explanation would suffice.

Increase in carbon atoms>increase in molecular weight> increase in dispersion forces> more energy needed to break the intermolecular bonds> higher temp

 

[nightweaver066]

re: HSC Chemistry Marathon Archive

I thought I never heard of dipoles and alkanes(/enes).

They are temporary and induced due to the movement of electrons lol

You never have to talk about this though.. Added it because Magical Kebab incorporated electrons in to his answer.

What he just posted up would be sufficient

Btw, i'll probably hang around and critique any long responses that people answer in this thread

 

[Magical Kebab]

re: HSC Chemistry Marathon Archive

They are temporary and induced due to the movement of electrons lol

You never have to talk about this though.. Added it because Magical Kebab incorporated electrons in to his answer.

What he just posted up would be sufficient

Wait so if I spoke about electrons and polarization would that be right?

 

[nightweaver066]

re: HSC Chemistry Marathon Archive

Wait so if I spoke about electrons and polarization would that be right?

No. The molecule isn't becoming more polarised, its just that there would be stronger temporarily induced dipoles.

I haven't seen this explanation in any marking scheme so i'd go with the other.

 

[hayabusaboston]

re: HSC Chemistry Marathon Archive

Describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass.

 

[nightweaver066]

re: HSC Chemistry Marathon Archive

Describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass.

That sounds like a dot point copy pasted..

Question:
State 2 examples of condensation polymers and explain their uses in relation to their properties.

 

[hayabusaboston]

re: HSC Chemistry Marathon Archive

That sounds like a dot point copy pasted..

State 2 examples of condensation polymers and explain their uses in relation to their properties.

Yea it is, isnt that what we're meant to be doing here? working on dotpoints?

 

[Sy123]

re: HSC Chemistry Marathon Archive

Yea it is, isnt that what we're meant to be doing here? working on dotpoints?

But that isn't fun at all, talking about pH6 neutral water is fun. I would hate this thread to turn into a rote fest where people just spit out their rote learnt answers... to generic questions. (but then again I didn't make this thread so...)

 

[nightweaver066]

re: HSC Chemistry Marathon Archive

But that isn't fun at all, talking about pH6 neutral water is fun. I would hate this thread to turn into a rote fest where people just spit out their rote learnt answers... to generic questions. (but then again I didn't make this thread so...)

It'd be good to perfect those answers though.

 

[hayabusaboston]

re: HSC Chemistry Marathon Archive

It'd be good to perfect those answers though.

Exactly, once you perfect those answers, for any new situation you will have so much info in ur head you can pick and choose what is applicable.

 

[theind1996]

re: HSC Chemistry Marathon Archive

But that isn't fun at all, talking about pH6 neutral water is fun. I would hate this thread to turn into a rote fest where people just spit out their rote learnt answers... to generic questions. (but then again I didn't make this thread so...)

But that's HSC Chemistry?

 

[nightweaver066]

re: HSC Chemistry Marathon Archive

Yea it is, isnt that what we're meant to be doing here? working on dotpoints?

I suppose that is one of the goals. It's usually exam style or challenging questions in these threads lol

 

[hayabusaboston]

re: HSC Chemistry Marathon Archive

I suppose that is one of the goals. It's usually exam style or challenging questions in these threads lol

Not to be arrogant or anything, but how can it be challenging when u've memorised every single dotpoint, because then whatever question u get u simply format the info in ur head according to the question. HSC chem and phys is easy in that respect, you just have to rote EVERYTHING there is to rote, plus calculations, which are pretty dang simple maths when it comes down to it haha

 

[nightweaver066]

re: HSC Chemistry Marathon Archive

Not to be arrogant or anything, but how can it be challenging when u've memorised every single dotpoint, because then whatever question u get u simply format the info in ur head according to the question. HSC chem and phys is easy in that respect, you just have to rote EVERYTHING there is to rote, plus calculations, which are pretty dang simple maths when it comes down to it haha

Challenging questions tend to be the concept-based ones, like the one Sy posted up earlier.

Even if one does memorise every single dot point, that doesn't lead to perfect answers to every question. Some questions require you to synthesise aspects from various dot points which can be difficult as you need to select the appropriate pieces of information and keep your answer concise.

 

[Sy123]

re: HSC Chemistry Marathon Archive

But that's HSC Chemistry?

I guess

 

[hayabusaboston]

re: HSC Chemistry Marathon Archive

Challenging questions tend to be the concept-based ones, like the one Sy posted up earlier.

Even if one does memorise every single dot point, that doesn't lead to perfect answers to every question. Some questions require you to synthesise aspects from various dot points which can be difficult as you need to select the appropriate pieces of information and keep your answer concise.

This made me realise something. You're right. We need to find as many of these multiple dotpoint questions as possible and assess ourselves on them.

 

[hayabusaboston]

re: HSC Chemistry Marathon Archive

I would tell you why this is not the case, but it would give the answer away haha.

EDIT: I didn't want to kill the thread this early, here is another question in the mean time while people think about it

Upon analysis of mass of a hydrocarbon was found to contain 82.6% Carbon and 17.4% Hydrogen. Calculate its empirical formula

aint this prelim stuff? it was in my yearly last year.

 

[Sy123]

re: HSC Chemistry Marathon Archive

aint this prelim stuff? it was in my yearly last year.

It would still fall under mole calculations wouldn't it? It tests ability to interpret the question and change from mass to moles.

It doesn't really matter anyway.

 

[bleakarcher]

re: HSC Chemistry Marathon Archive

But that isn't fun at all, talking about pH6 neutral water is fun. I would hate this thread to turn into a rote fest where people just spit out their rote learnt answers... to generic questions. (but then again I didn't make this thread so...)

I agree with you Sy but as much as I hate to say it, we must have a fair mixture.