AQA CHEM2 ~ May 23rd 2012 ~ AS Chemistry

Reply 780

Ayakashi

Original post by berryripple

I got my result accurate enough to get the highest accuracy mark, so can I assume that's 54/60 then? :lolwut:

yea I guess.

Reply 781

cheesecake11

2

do we need to know about hetergenous and homogenous catalyst? the bitch aint even on the spec mannnnnnnn. (hehe)(tehe)(lele).(excuse me the oddness, just had a bar of nutrigrain, awesomes with an apple apple filled centre! moister than the beach baby, yeeah)

Reply 782

Zytex

Original post by Jack_Smith

Can someone help me with this :
Jan 11 qs 3d..im not sure where this is mentioned in the book :/
http://store.aqa.org.uk/qual/gce/pdf/AQA-CHEM2-W-QP-JAN11.PDF

Answers:

Reagent: Acidified Potassium Dichromate (Acidified K2Cr2O7)

Observation with butan-2-ol(l): Colour change of orange/red to green

Observation with 2-methylpropan-2-ol(l): No reaction/No colour change/Colour stays orange|red.

Butan-2-ol is a secondary alcohol and is oxidised by the Acidified K2C2O7(primary and secondary alcohols react with acidified potassium dichromate)

2-methylpropan-2-ol is a tertiary alcohol and cannot be oxidised by the acidified potassium dichromate.

Original post by cheesecake11

do we need to know about hetergenous and homogenous catalyst? the bitch aint even on the spec mannnnnnnn. (hehe)(tehe)(lele).(excuse me the oddness, just had a bar of nutrigrain, awesomes with an apple apple filled centre! moister than the beach baby, yeeah)

In my Nelson Thornes textbook there are two line definitions for each. If you have the textbook, page 141.

Heterogeneous catalysts: where the catalyst is in a different phase to the reactants - usually a solid catalyst and liquid or gaseous reactants.

Homogeneous catalysts: where the catalyst and reactants are in the same phase.

(edited 11 years ago)

Reply 783

Hdizzle

9

Original post by cheesecake11

do we need to know about hetergenous and homogenous catalyst? the bitch aint even on the spec mannnnnnnn. (hehe)(tehe)(lele).(excuse me the oddness, just had a bar of nutrigrain, awesomes with an apple apple filled centre! moister than the beach baby, yeeah)

not that i know of
never have i come across the term whilst doing the past papers

Reply 784

Hdizzle

9

Original post by Zytex

Answers:

Reagent: Acidified Potassium Dichromate (Acidified K2Cr2O7)

Observation with butan-2-ol(l): Colour change of orange/red to green

Observation with 2-methylpropan-2-ol(l): No reaction/No colour change/Colour stays orange|red.

Butan-2-ol is a secondary alcohol and is oxidised by the Acidified K2C2O7(primary and secondary alcohols react with acidified potassium dichromate)

2-methylpropan-2-ol is a tertiary alcohol and cannot be oxidised by the acidified potassium dichromate.

In my Nelson Thornes textbook there are two line definitions for each. If you have the textbook, page 141.

Heterogeneous catalysts: where the catalyst is in a different phase to the reactants - usually a solid catalyst and liquid or gaseous reactants.

Homogeneous catalysts: where the catalyst and reactants are in the same phase.

?!

by phase do you mean 'states' ?

Reply 785

Zytex

Original post by Hdizzle

?!

by phase do you mean 'states' ?

Yes, I would put states if I was writing that down during an exam, I just copied the textbook's definition.

Reply 786

ElMoro

18

Original post by Hdizzle

?!

by phase do you mean 'states' ?

Phases and states are different things

Reply 787

berryripple

Original post by ElMoro

The raw marks are out of 50:
38 for the ISA (30 for the actual paper and 8 for that specific experiment), 12 for the PSA

Here's the raw-->UMS for the last 3 years :smile:

Ahh! I get it now. I got 34/38 plus 12. Thanks Elly! :h:

Reply 788

Picture~Perfect

19

Can somebody list the main reagents we need to know about.

I know:
Acidified potassium dichromate gently oxidises alcohols
Silver nitrate is a test for halogens
Concentrated ammonia distinguishes between silver bromine and silver iodine.
Tollen's/Fehling's reagents distinguish between aldehydes and keytones.

I'm I missing anything?

Reply 789

cheesecake11

2

what is the oxidation state of oxygen in compounds with fluorine, +2 or +1?

Reply 790

cheesecake11

2

Original post by Picture~Perfect

Can somebody list the main reagents we need to know about.

I know:
Acidified potassium dichromate gently oxidises alcohols
Silver nitrate is a test for halogens
Concentrated ammonia distinguishes between silver bromine and silver iodine.
Tollen's/Fehling's reagents distinguish between aldehydes and keytones.

I'm I missing anything?

silver nitrate must be acidified.the amount of times i missed that out :facepalm:

Reply 791

Spellstheend

Original post by cheesecake11

what is the oxidation state of oxygen in compounds with fluorine, +2 or +1?

I'm guessing +1 as F has -1 so to balance that to 0 it'd have to be +1

could be wrong

Reply 792

ElMoro

18

Original post by cheesecake11

what is the oxidation state of oxygen in compounds with fluorine, +2 or +1?

Original post by Spellstheend

I'm guessing +1 as F has -1 so to balance that to 0 it'd have to be +1

could be wrong

Completely depends on the compound, F is always -1 so:
- In OF₂, O has oxidation state +2
- In O₂F₂, O has oxidation state +1

Reply 793

ElMoro

18

Original post by berryripple

Ahh! I get it now. I got 34/38 plus 12. Thanks Elly! :h:

That's good, you'll be looking at between 48-52 UMS based on the previous years :smile:

Reply 794

Zytex

Anyone have any idea what the grade boundaries for EMPAs (externally marked practical assessments) are like? Our school originally were doing ISAs but then bailed for some reason.

Reply 795

cheesecake11

2

when writing the simple ionic equations is it necessry to place the (aq) , i mean the states?
so what i get from past papers-always balance equations??? apart from alcohol oxidation with dilute sulphuric acid?

Reply 796

cuckoo99

13

Original post by Mystic Creature

I said that 70% of the marks are from equations AND organic chemistry, and mechanisms come under organic chemistry dude so yeah. And most of the 'various experiments' are from the redox and halogens chapter, where the most important thing is knowing the equations (and observations are kinda part of that too). But fine, maybe still a bit of an exagerration, probably about 60%. Theres normally not very much on spectroscopy, definitions are something you should know anyway, and tbh, kinetics and equilibria isnt really that challenging.

I read this back and sorry if it sounds like im having a go at you, i really wasnt lol :s-smilie: