VCE Chemistry Question Thread

[everythangcoZ]

What exam is this on? I would assume this reaction is occurring at SLC, thus both are at a liquid state.
Yes it is fine. You have just used a dilution factor instead.

2017 exam, but it doesn't state it is at SLC so I'm not sure, but does that mean at SLC all alcohols and carboxylic acids are liquid (which would make sense duh lolll), and of course going by the states in the data booklet at SLC aswell.

[Bri MT]

Hey guys,
I often see this sort of thing come up, but how do you know the states for carboxylic acids. My teacher says they're usually aqueous and same with the alcohol, but in the exam report for this question they are liquid?
Do you take it literally in real life setting as liquids (don't know if that makes sense lol) just unsure.

remember that in esterification you don't want much water around since that would reduce your yield (water is on the products side of the reaction). I'm pretty sure this would be their reasoning here.  This is also why you need to specify sulphuric acid as being either liquid or concentrated.

imo SLC isn't all that relevant to this discussion since we aren't debating whether it would be a gas but instead we're talking about whether it's in aqueous solution (I.e. with a bunch of water).

[Coolgalbornin03Lo]

In a calorimeter prac what are some systematic errors? I’ve come up with “poor insulation” but how can that be resolved?

[everythangcoZ]

In a calorimeter prac what are some systematic errors? I’ve come up with “poor insulation” but how can that be resolved?

another systematic error could be, if using something such as a spirit burner which involves great heat loss if positioned away from the container: moving the container closer to the flame to help minimise heat loss

Another one could have to do with the thermometer giving incorrect readings of temp. You could maybe even discuss one about the electrical heater as it may not be working, basically anything that you would have to physically change if you want to repeat the experiment.

with poor insulation, you can suggest insulating the container with something such as styrofoam, or anything that is a good insulator to help minimise heat loss

not 100% sure on all of these but correct me if im wrong

[Coolgalbornin03Lo]

Thanks so much everythangcoZ!

In electrolysis and galvanic cells which electrical terminal are the anode and cathode connected to?

Also how come for electrolysis the current which has to be applied  is MORE than the voltage of cell?

[Chocolatemilkshake]

If you use a molar mass from the periodic table with 2 significant figures (such as hydrogen) does that mean your answer also has to be to only 2 significant figures (sounds like a simple Q but there are tonnes of company exams that don’t do this so I was wondering whether to or not)
Thanks!

[everythangcoZ]

If you use a molar mass from the periodic table with 2 significant figures (such as hydrogen) does that mean your answer also has to be to only 2 significant figures (sounds like a simple Q but there are tonnes of company exams that don’t do this so I was wondering whether to or not)
Thanks!

I don't think so, I'm pretty sure you base your sig figs on the values you are given on the exam paper, so as long as your answer is correct to the lowest sig fig provided in that exam question you should be fine

[ActivationEnergy]

Hi guys,
What is the best explanation as to why amylopectin is more soluble than amylose? Is it just because amylopectin is branched and has a lot more free hydrogens than amylose?

[everythangcoZ]

Hi guys,
What is the best explanation as to why amylopectin is more soluble than amylose?

Hey so, generally this would just be the fact that amylopectin is a branched structure, meaning that is has more OH groups exposed to make hydrogen bonds with water and become soluble, however amylose is a straight chain molecule and can coil into a helix like structure where the OH groups are packed tightly inside and are not in contact with water, therefore becoming less soluble in water. Whereas, in comparison to amylopectin it has a branched structure making it less likely to coil, thus having more OH groups exposed to form hydrogen bonds with water.

Not sure if this is the BEST explanation but that is what i could gather and learn from my textbook

[aspiringdocxxxx]

will the last question always be scenario based? that seems to be the case for the past few years but I’m not sure!

[Geoo]

will the last question always be scenario based? that seems to be the case for the past few years but I’m not sure!

Since 2017, it always has been. I don't see VCAA changing it up this year as they have been so consistent for the past 3 years, so I don't see why they would this year.

[emonerd]

Thanks so much everythangcoZ!

In electrolysis and galvanic cells which electrical terminal are the anode and cathode connected to?

Also how come for electrolysis the current which has to be applied  is MORE than the voltage of cell?

Hey there! In electrolysis, the negative electrode which is the cathode will be connected to the negative terminal of the power source. For the positive electrode, the anode, it will be connected to the positive terminal. So positive to positive, negative to negative. You won't have to worry about which terminal it's connected to for galvanic, as galvanic cells do not require an input of energy in order for the half reactions to occur.

As for why the voltage must be greater than the difference between the reductant and oxidant, (this might not be the best explanation - sorry!) but in electrolysis essentially what you are doing is FORCING the electron flow. In order to do this, you have to have a voltage that is greater than the voltage that would normally be produced by the cell. If the voltage is not high enough, the electrons will not be able to be forced towards the cathode.

Hope this kinda makes sense

[Bri MT]

If you use a molar mass from the periodic table with 2 significant figures (such as hydrogen) does that mean your answer also has to be to only 2 significant figures (sounds like a simple Q but there are tonnes of company exams that don’t do this so I was wondering whether to or not)
Thanks!

In the past they have accepted sig figs either including the period table values or not

[kxyaa]

Can we write in 2B pencil for Section B?

[Bri MT]

Can we write in 2B pencil for Section B?

People have reported doing this and it being fine but I would personally only use greylead for diagrams/figures because otherwise I'd be stressed about it. At the very least I recommend bringing in pens in case you are given a specific instruction to use pen.

It looks like the exam doesn't specify blue or black pen this year.
https://www.vcaa.vic.edu.au/Documents/exams/exam-covers/chemistry-cov-mc.pdf