VCE Chemistry Question Thread

[zxcvbnm18]

How come they are one of the worst?

[sweetiepi]

Do a lot of schools use qat for their sacs?

Not sure that a lot do, however I do remember doing a lot of QAT sacs in my time, and I don't necessarily think they were that bad

[MandhreeE]

Hey guys i was wondering if someone could help me out with this question.

So we did a prac on determining the water of hydration of CuSO4.xH2O and after dehydrating the mixture we had to work out a mole ratio for copper (II) sulfate: water. I got 1:3 doing my prac but the theoretical value was meant to be 1:5 i was wondering if anyone could suggest why my results were wrong? like what are the possible errors that could have occured.

thank you so much in advance

[deStudent]

For this http://m.imgur.com/JSMu6q0
Part b) is the unit M^-0.5 or positive? I had negative, answer had positive..

Thanks

[Shadowxo]

For this http://m.imgur.com/JSMu6q0
Part b) is the unit M^-0.5 or positive? I had negative, answer had positive..

Thanks

I think you're right with the negative Maybe they had 1/M^1/2?

[NAT0003]

Do chemistry and maths methods share any similarities

[sweetiepi]

Do chemistry and maths methods share any similarities

Off the top of my head, there are chemical formulas that require log (such as pH), which is covered in at least methods, as well as rearrangements of formulas which seem is fairly basic, once you get the hang of it.
I know people who did chem and didn't so methods, so even if you don't do methods, you should be fine.

[vcestressed]

Unreactive group of elements are called noble gases. One example is neon. Explain why noble gases are unreactive.
I wrote 'full valence shell' but the answer sheet clearly says 'no mark for full valence shell'.
The only acceptable answers are:
- stable electron configuration
or
- have stable valence shell
Why? 
Thanks

[sweetiepi]

Unreactive group of elements are called noble gases. One example is neon. Explain why noble gases are unreactive.
I wrote 'full valence shell' but the answer sheet clearly says 'no mark for full valence shell'.
The only acceptable answers are:
- stable electron configuration
or
- have stable valence shell
Why? 
Thanks

This is most likely due to wording requirements. However, I define noble gases as have stable valence shells, as they have a full valence shell and fulfill the octet rule (up to about element 20, Calcium, before getting wacky with the electron configurations ).

(Excuse any typos- I'm currently on a tram home/I'll fill out with more detail as soon as I can)

[vcestressed]

This is most likely due to wording requirements. However, I define noble gases as have stable valence shells, as they have a full valence shell and fulfill the octet rule (up to about element 20, Calcium, before getting wacky with the electron configurations ).

(Excuse any typos- I'm currently on a tram home/I'll fill out with more detail as soon as I can)

Thanks, so saying it is 'stable' rather than 'full' is better due to its terminology?

[sweetiepi]

Thanks, so saying it is 'stable' rather than 'full' is better due to its terminology?

Most welcome and glad to be of help!
Yep! Generally the more scientific terminology is favoured to plain English.

[seth]

Hey all, does a question usually say if reactants are in excess or do you always have to check? Thanks for all help.

[sweetiepi]

Hey all, does a question usually say if reactants are in excess or do you always have to check? Thanks for all help.

Generally it won't say if a reactant is in excess. (except for when it is a combustion reaction, where it indicates if there is or isn't enough oxygen)
I'd highly recommend making it a habit to always check.

[monashvivek]

Thank you so much

[seth]

Generally it won't say if a reactant is in excess. (except for when it is a combustion reaction, where it indicates if there is or isn't enough oxygen)
I'd highly recommend making it a habit to always check.

Thank you

Another question: why is the cathode usually identified from the anode by its higher position in the electrochemical series? From my knowledge, the cathode is the site where reduction occurs, and the higher up the series, the stronger the oxidation strength. From this logic, shouldn't the cathode be lower than the anode in the series?