VCE Chemistry Question Thread

[nadiaaa]

Hey!
So to get delta H, you subtract the inital energy from the final energy (in this case   -100-250)

Activation Energy is calculated by the peak energy (450) minus the reactant energy (250). You should get answer B

Omg im so so so sorry, i attached the wrong image. This was the question , thanks for that though 

[larissaaa_]

Throwin' it back to year 11 chemistry but why are the electrons in energy levels closest to the nucleus the ones that have the lowest energies?

[Sine]

Omg im so so so sorry, i attached the wrong image. This was the question , thanks for that though 

chlorine is produced at 4M and oxygen with 0.1M  something you just need to remember.

[blacksanta62]

Throwin' it back to year 11 chemistry but why are the electrons in energy levels closest to the nucleus the ones that have the lowest energies?

I think it's because less energy is required by the nucleus to keep them in orbit around it, hence they have a low energy level, making them more stable than those further out from the nucleus.

Really have forgotten though so if I'm wrong someone please correct me

[bananabreadbelle]

I think it's because less energy is required by the nucleus to keep them in orbit around it, hence they have a low energy level, making them more stable than those further out from the nucleus.

Really have forgotten though so if I'm wrong someone please correct me

From what I think/remember - the nucleus of an atom is inherently positively charged (since protons are positive and neutrons have no charge), therefore since electrons are negatively charged: there is an electrostatic force of attraction between the nucleus and the electrons.

So how I think of it is, think of a magnet and a piece of metal: it's 'natural'/takes minimal effort and energy for the magnet and metal to be attracted and therefore close to each other, but it takes effort and energy to pull the magnet and metal apart from each other.

So in sort of the same way, if you pull the electrons that all want to be close to the nucleus (in the 'inner shell'/ground state) farther away from the nucleus (to outer shells) it takes more energy and are therefore at 'higher energy levels'.

Does that make sense?   
(Feel free to correct/improve my flawed analogy or clarify if I've misunderstood anything!)

[Adequace]

Hi,

Can someone see what I did wrong here http://imgur.com/a/mMLmf. I'm not sure why the book's answer still has Pb in balanced equation.

Also, I forgot the -2 on SO4 in my final lines before I took this photo so don't worry about that mistake.

Tyty

[sweetcheeks]

Hi,

Can someone see what I did wrong here http://imgur.com/a/mMLmf. I'm not sure why the book's answer still has Pb in balanced equation.

Also, I forgot the -2 on SO4 in my final lines before I took this photo so don't worry about that mistake.

Tyty

By the look of it the PbS and PbSO4 are both solid. It is common for aqueous compounds such as potassium permanganate to be written simply using the permanganate ion, as it dissociates in the water, but it is not the same for solids.

[lzxnl]

 I suggest you have an idea of solubility for the salts you come across commonly in VCE. So like, sulfates, chlorides, nitrates, alkaline metal salts, oxides, carbonates

[Gogo14]

Do you maintain the same sig figs in calculation,
or do you just put the sig figs in the final calculation?

[HopefulLawStudent]

Asked to "draw the semistructural formula of compound A".

How do they get their answer of CH3COOCH3? The splitting doesn't seem to work?

[Adequace]

Thanks sweetcheeks and lzxnl. So since they're solids but don't change the oxidation numbers of S, is my working still correct when I find how many electrons an S (atom?) loses when it undergoes oxidation? I pretty much ignored the Pb's.

[sweetcheeks]

@HopefulLawStudent

It took me a while, but look at the cluster of 5 peaks. Notice something is off. The tallest peak should always be in the middle, however there is a really tall peak on the left. This is actually a singlet. So we have a quartet, a singlet and a triplet. This matches ethyl ethanoate.

[sweetcheeks]

Thanks sweetcheeks and lzxnl. So since they're solids but don't change the oxidation numbers of S, is my working still correct when I find how many electrons an S (atom?) loses when it undergoes oxidation? I pretty much ignored the Pb's.

Yep, your working is fine. Just out of curiosity, have you heard/used the KOHES method before?

[HasibA]

quick q- what is the hardest chem exam (both VCAA and non vcaa) in terms of cut offs/general difficult? i know this is vague, but thanks

[sweetcheeks]

quick q- what is the hardest chem exam (both VCAA and non vcaa) in terms of cut offs/general difficult? i know this is vague, but thanks

The 2014 VCAA exam allowed up to 20 marks to be dropped. There are a lot of difficult/unseen concepts in this exam (Parts Per Million) and logical thinking questions.

I have found the NEAP to be the most difficult, I have dropped the most marks on them compared to other exams. However, I have noticed that there are some thing unrelated to the study design.