VCE Chemistry Question Thread

[TFAnime123]

When writing chemical equations, what is the state typically used for carboxylic acid and alcohols? Does this change for varying situations/conditions?

[papaya seed]

I know this is kind of last minute, but what are the main acids and bases that we need to know the strengths of? - e.g NaOH = strong base and HCl = strong acid

[-elcee]

PV=NRT uses 100 kpa as the standard right ?

[hmdeadas]

Do i have to know about the simple bond types? eg. dispersion, hydrogen etc..
As i have studied everything but have completely forgot what they are and how they look.. any way to know when their are each forces / bonds?

ALSO how important are reaction pathways? I do not understand them and cannot seem to stick them in my head? any help? please

[Phenomenol]

when giving units in the question, not referring to significant figures just things like mol-1 or mol/g , i never know which one to use. How much marks will i lose for stating the incorrect units? Is it like S.I where i lose 1 mark overall?

Thanks

Do you mean between g/mol and g mol^-1? If so, they are the same.
If your units are incorrect you may lose one mark for that question.

When writing chemical equations, what is the state typically used for carboxylic acid and alcohols? Does this change for varying situations/conditions?

Depends. Both carboxylic acids and alcohols are usually either liquid or aqueous.

I know this is kind of last minute, but what are the main acids and bases that we need to know the strengths of? - e.g NaOH = strong base and HCl = strong acid

Strong acids: HCl and H₂SO₄
Strong bases: Hydroxides

PV=NRT uses 100 kpa as the standard right ?

Whenever you need to use PV=nRT, the question will provide all the necessary values. You will never need to conjure up any numbers based on what might be for standard conditions.

Do i have to know about the simple bond types? eg. dispersion, hydrogen etc..
As i have studied everything but have completely forgot what they are and how they look.. any way to know when their are each forces / bonds?

ALSO how important are reaction pathways? I do not understand them and cannot seem to stick them in my head? any help? please

Yes, ideally. It will help you explain physical properties of compounds (i.e. melting and boiling points)
Each type of interaction can be identified by what atoms are participating, not how it "looks".

I would hazard a guess and say questions about reaction pathways could take up anywhere between 6-10 marks on the exam. If you can at least remember how addition + substitution + oxidation + esterification differ from each other, that will help you a lot.

Best of luck to all! Remember that you should not look back after the exam is finished!

[lzxnl]

Depends. Both carboxylic acids and alcohols are usually either liquid or aqueous.

Strong acids: HCl and H₂SO₄
Strong bases: Hydroxides

Whenever you need to use PV=nRT, the question will provide all the necessary values. You will never need to conjure up any numbers based on what might be for standard conditions.

Best of luck to all! Remember that you should not look back after the exam is finished!

Will add that nitric acid is also considered a strong acid. I doubt you'll run into these, but like HCl, HBr and HI are strong too.
Note: HSO₄^- is not strong!

Also, for pV = nRT, either you measure pressure in kPa and volume in litres, or pressure in Pa and volume in cubic metres. Pick one pair.

[Nosheep]

so are there still no solns guys?

[Guideme]

Can someone please do the 32 g and h .
For some reason I could do a,d,c but I couldn't do the rest :/

Thanks in advanced

[VanillaRice]

(Image removed from quote.)

Can someone please do the 32 g and h .
For some reason I could do a,d,c but I couldn't do the rest :/

Thanks in advanced

What progress have you made on the questions so far? What are the half equations you have gotten from the overall reaction?
Please post your working (or tell us what part you're stuck on) so we can see exactly what part you require help with

[A TART]

Hi

I've been able to answer the question below through guessing and checking multiple times. Is it just the question or is there a trick to finding which reaction the H20 species belongs to (coz there's like 4)?
https://i.imgur.com/8PxJzap.png

PS: I got C

[keltingmeith]

Hi

I've been able to answer the question below through guessing and checking multiple times. Is it just the question or is there a trick to finding which reaction the H20 species belongs to (coz there's like 4)?
https://i.imgur.com/8PxJzap.png

PS: I got C

The "trick" is to use the electrochemical series - you should be able to quickly use the electrochemical series to figure out if a reaction is or isn't spontaneous, the hard part should just be finding all the right compounds. You are correct, though - the answer is C.

[Vaike]

Hi
...
PS: I got C

Hi there! Just to elaborate on keltingmeith's answer, whenever a question says "under standard conditions", take that as a hint to use the EC series. We can quite clearly see, using the EC series (https://imgur.com/a/FxgMK), that both H₂S and H₂O both act as reductants, and hence, must react with oxidising agents. This rules out Cu(s) and Mg(s). Then, use the relative positions of Cl₂(g) and Ag⁺(aq) to determine which reacts with H₂S but not H₂O.

[vcestressed]

Hey!! Just a quick question on increasing the pressure to increase reaction rate.
I understand that increasing pressure = increased chance of particle collisions to form products = increase in overall reaction rate.
I also read this:
"NOTE: Changing the pressure of chemical reactions involving liquids and solids won't result in an increase in reaction rate."
I don't understand what this means . .Can someone please explain?

[cookiedream]

Hey!! Just a quick question on increasing the pressure to increase reaction rate.
I understand that increasing pressure = increased chance of particle collisions to form products = increase in overall reaction rate.
I also read this:
"NOTE: Changing the pressure of chemical reactions involving liquids and solids won't result in an increase in reaction rate."
I don't understand what this means . .Can someone please explain?

Hello!
Well, what I think of pressure is that it is a measure of how many particles are hitting the walls of a container at a time. High pressure means a lot of particles hitting the walls for a period of time, and vice versa for low pressure. Thus, an increase or decrease in pressure itself is often not a determining factor in reaction rate. Rather, it is the condition which causes a change in the pressure (e.g. an increase in temperature = particles moving quickly = more particles hitting the container walls at a time = higher pressure. In this case, it would be the rise in temperature which increases reaction rate, not the increase in pressure).

[Eric11267]

Hey!! Just a quick question on increasing the pressure to increase reaction rate.
I understand that increasing pressure = increased chance of particle collisions to form products = increase in overall reaction rate.
I also read this:
"NOTE: Changing the pressure of chemical reactions involving liquids and solids won't result in an increase in reaction rate."
I don't understand what this means . .Can someone please explain?

Pressure only affects gaseous reactants and will have no effect on the collisions between liquids and solids.