HSC 2012-2015 Chemistry Marathon (archive) (7 Viewers)

[Fiction]

re: HSC Chemistry Marathon Archive

Relate volume/pressure for ideal gases.

Thunderstorm is partially correct. Try to find his mistake.

This is purely guessing, but is he right in assuming that the equilibrium will shift to the side with the least no. of gas molecules as the equilibrium seeks to increase volume, but he is wrong in assuming that the equilibrium wishes to become equimolar?

 

[Librah]

re: HSC Chemistry Marathon Archive

adfalsdjfk

Can someone please point out the difference between the situation as illustrated by HeroricPanda and one where inert gas doesn't affect equilibrium? I'm not seeing the differences. Why does 'constant pressure' rather than just 'pressure' affect anything? Thanks.

Consider constant pressure and constant volume. Inert gases will not affect an equilibrium at constant volumes.

 

[InteGrand]

re: HSC Chemistry Marathon Archive

PV = nRT

 

[Thunderstorm]

re: HSC Chemistry Marathon Archive

Hawkrider jumped off the bandwagon 'unlike' haha

 

[Thunderstorm]

re: HSC Chemistry Marathon Archive

Is it a volume increase thus a pressure decrease? If so, system shifts right. If pressure has to stay constant, then volume would increase yes?

 

[InteGrand]

re: HSC Chemistry Marathon Archive

Is it a volume increase thus a pressure decrease? If so, system shifts right. If pressure has to stay constant, then volume would increase yes?

If you hold everything else constant and increase volume, yes, pressure decreases.

I'm not sure what you mean by the last question (but maybe that's because it is related to some earlier posts, which I haven't read).

 

[hawkrider]

re: HSC Chemistry Marathon Archive

Hawkrider jumped off the bandwagon 'unlike' haha

pls

Is it a volume increase thus a pressure decrease? If so, system shifts right. If pressure has to stay constant, then volume would increase yes?

yes, that's right. if you have a container of apples where the volume has decreased, then the pressure would increase as the apples would struggle to find room to move around more if the area was constricted. so in this case, we want to decrease the pressure, to minimise the disturbance

not sure about your second Q, don't understand what you mean exactly lol

 

[Librah]

re: HSC Chemistry Marathon Archive

Is it a volume increase thus a pressure decrease? If so, system shifts right. If pressure has to stay constant, then volume would increase yes?

Yes, that was the mistake, the equilibrium should shift to the right initially.

 

[Drsoccerball]

re: HSC Chemistry Marathon Archive

Whats the difference between systematic name, common name, preferred name, IUPAC name ect... and any way of remembering it?

 

[Kaido]

re: HSC Chemistry Marathon Archive

Systematic - Ethene
Common - Ethylene
Preferred - (Doesn't matter)
IUPAC (official naming) - Ethene

I think

 

[Ekman]

re: HSC Chemistry Marathon Archive

Systematic Name: Chloroethene
Preferred/Common Name: Vinyl Chloride
IUPAC Name: 1-Chloroethene

 

[Kaido]

re: HSC Chemistry Marathon Archive

For IUPAC ekman, is it really 1-chloroethene?
There can be no other position for the chloride anyway, so shouldn't it be just chloroethene o.o

 

[teridax]

re: HSC Chemistry Marathon Archive

pretty much what kaido and ekman said is right

but as for remembering it, just rote lol

the section 1-3 of PoM is crap

really? i don't do chem anymore as i dropped it in year 11 but stuff like cracking, surely you'd have to understand it

 

[hawkrider]

re: HSC Chemistry Marathon Archive

really? i don't do chem anymore as i dropped it in year 11 but stuff like cracking, surely you'd have to understand it

nope, all you have to know is that there's thermal and catalytic cracking - they don't even ask why it works lol - it's pretty bad aha

 

[Ekman]

re: HSC Chemistry Marathon Archive

For IUPAC ekman, is it really 1-chloroethene?
There can be no other position for the chloride anyway, so shouldn't it be just chloroethene o.o

Well I was always taught to label where the function group is when there is 2 or more carbons. I understand how 1-chloromethane might not need it, but I believe 1-chloroethene will need it. Then again it doesn't really matter since these types of questions usually come up as MC where its just between Systematic and Preferred/Common name.

 

[swagswagyoloswag]

re: HSC Chemistry Marathon Archive

5 marks
Usnig specific example, explain how the structure of your chosen plastic allows it to be used for one of its current applications.

 

[someth1ng]

re: HSC Chemistry Marathon Archive

Systematic Name: Chloroethene
Preferred/Common Name: Vinyl Chloride
IUPAC Name: 1-Chloroethene

IUPAC is just chloroethene.

Anyway, systematic name means that it's named strictly to the naming conventions. Common name is what it's normally called in everyday talk. IUPAC is what I would call an international organisation that represents chemists around the world - their naming usually the same as the systematic name but it is sometimes changed to something more common.

 

[someth1ng]

re: HSC Chemistry Marathon Archive

adfalsdjfk

Can someone please point out the difference between the situation as illustrated by HeroricPanda and one where inert gas doesn't affect equilibrium? I'm not seeing the differences. Why does 'constant pressure' rather than just 'pressure' affect anything? Thanks.

If you pump more argon into the system (or any gas that doesn't react with anything in the vessel) while keeping volume constant, equilibrium doesn't change. If you pump argon into the system and the system expands as a result, then the equilibrium will change.

To explain why this happens, you need to start with what partial pressure is and the simplest way to put it is that it what the pressure would be if it were the only gas in the reaction vessel (ie everything else removed). Now, for a reaction to occur, two of the reactants need to collide - that's why increasing temperature increases reaction rate (more possible successful collisions). If the partial pressures is the same, the odds of a collision must also be the same, regardless of whether the inert gas is there or not (remember, the same can also be applied in the opposite direction). That's why the equilibrium is unchanged if you just have some random gas pumped in at fixed volume - the pressure increases but the rate of reaction does not.

 

[Drsoccerball]

re: HSC Chemistry Marathon Archive

Why can't flame test be done on anions? 2 Marks (only 2015'ers answer please ) lets get this shit running again

 

[BlueGas]

re: HSC Chemistry Marathon Archive

Why can't flame test be done on anions? 2 Marks (only 2015'ers answer please ) lets get this shit running again

Anions are negatively charged and cannot be identified by flame tests, this is because they don't want to gain energy (hence negative).