VCE Chemistry Question Thread

[RazzMeTazz]

What would be the two possible products formed  in the reaction of but-2-ene with hydrogen bromide?

Thanks! 

[keltingmeith]

What would be the two possible products formed  in the reaction of but-2-ene with hydrogen bromide?

Thanks! 

2-bromobutane and 3-bromobutane (which is 2-bromobutane, so...). The double bond is cleaved, and the hydrogen and bromide will both append themselves to a carbon. The carbon that each go to, however, is beyond VCE. (if you want to know which one each goes to, google Markovnikov's rule. Note that in this case, only 2-bromobutane forms, so it's not an issue)

[Sundal]

By saying "alkanols can be oxidised to form carboxylic acids" is it specifically referring to the Carbon atom being oxidised?

Thank you all.

[lzxnl]

By saying "alkanols can be oxidised to form carboxylic acids" is it specifically referring to the Carbon atom being oxidised?

Thank you all.

Generally, organic oxidations or reductions refer to oxidations or reductions of the carbon.

[KingDrogba]

What total sac scores do you need for an A+ in each unit? Out of 100

[RazzMeTazz]

What would be the semi-structural formula for ethyl methanoate?

Would it be CHOOCH2CH3 or COOHCH2CH3 ?

[Splash-Tackle-Flail]

What would be the semi-structural formula for ethyl methanoate?

CH3CH2OH is ethanol, and methanoic acid is HCOOH, when they undergo esterification, water is released. Does this help?

Spoiler

CH3CH2OOCH iirc

Edit: you can also write it with the methanoic part first if you want I think (i.e HCOOCH2CH3)

[RazzMeTazz]

CH3CH2OH is ethanol, and methanoic acid is HCOOH, when they undergo esterification, water is released. Does this help?

Spoiler

CH3CH2OOCH iirc

Edit: you can also write it with the methanoic part first if you want I think (i.e HCOOCH2CH3)

Yeah, that helped a lot! Thankyou

[Splash-Tackle-Flail]

What total sac scores do you need for an A+ in each unit? Out of 100

Going of last year:
Unit 3 A+ cutoff is 95/100
Unit 4 A+ cutoff is 91/100

http://www.vcaa.vic.edu.au/Documents/statistics/2014/section3/vce_chemistry_ga14.pdf for more stats, and don't forget they get scaled based on exam performance anyway

[knightrider]

for the formula of lead(IV)oxide i got but the answers got

How did they get that ?

[grannysmith]

for the formula of lead(IV)oxide i got but the answers got

How did they get that ?

Pb⁴⁺ + 2O^2- --> PbO₂

[scarletmoon]

How would you prove that sulfuric acid is a catalyst and not a reactant in a reaction?
(Salicylic acid and acetic anhydride)

[IndefatigableLover]

for the formula of lead(IV)oxide i got but the answers got

How did they get that ?

Adding onto what grannysmith has written, in the name they've stated lead (IV) oxide where the number indicates the valency of that particular element (that is lead has a valency of +4)
You'll come across other examples as well such as Copper for instance!

[keltingmeith]

How would you prove that sulfuric acid is a catalyst and not a reactant in a reaction?
(Salicylic acid and acetic anhydride)

a) Experimentally, you'll notice that the experiment only starts once sulfuric acid is added.
b) When writing out the chemical equation, it can be noted that H2SO4 does not appear in the product, and so must be a catalyst.

Both of these combined should be sufficient.

[knightrider]

Adding onto what grannysmith has written, in the name they've stated lead (IV) oxide where the number indicates the valency of that particular element (that is lead has a valency of +4)
You'll come across other examples as well such as Copper for instance!

yep thanks IndefatigableLover 

but the thing i dont get is doesnt the valency of 4 from the lead then become the oxygen subscript in order to balance the overall charge?

So wouldnt it be   why is it then  ?