AQA CHEM5 A2 Chemistry - 19th June 2013

Reply 820

loknath

7

anybodys teachers made predictions on whats going to come up :smile:

Reply 821

Dalts

1

Original post by loknath

anybodys teachers made predictions on whats going to come up :smile:

To be honest, the curriculums so small and the exams so big that its likely they'll be able to ask everything.

Reply 822

Mathletic

Original post by candyhearts

Also, does anyone have any tips on trying to memorise periodicity and the equations for the catalysts

Do the questions in the nelson thornes / cgp revision guide if you have them and then go through all past papers and pull out periodicity questions and answer them, do this again a few nights before the exam too and im sure youl get an easy 9 marks or so :smile:

Reply 823

itssochaotic

can someone explain why Njune 2011 6d i has given the reacting ratio of Mno4 to C2O4 ^2- as 3:5 when the equations balance to give a 2:5 ratio and also the textbook gives it in a 2:5 raito :P the mark scheme couldnt be wrong could it?

Also this thread is kinda dead considering how close to the exam it is :P

Reply 824

Dirtybit

20

Original post by itssochaotic

can someone explain why Njune 2011 6d i has given the reacting ratio of Mno4 to C2O4 ^2- as 3:5 when the equations balance to give a 2:5 ratio and also the textbook gives it in a 2:5 raito :P the mark scheme couldnt be wrong could it?

Also this thread is kinda dead considering how close to the exam it is :P

It will get alive like a few days close to the exam and after too :wink:

Reply 825

DELETED ACCOUNT

15

Original post by itssochaotic

can someone explain why Njune 2011 6d i has given the reacting ratio of Mno4 to C2O4 ^2- as 3:5 when the equations balance to give a 2:5 ratio and also the textbook gives it in a 2:5 raito :P the mark scheme couldnt be wrong could it?

Also this thread is kinda dead considering how close to the exam it is :P

We still have just under 3 weeks left! :biggrin:

Reply 826

Dalts

1

Original post by itssochaotic

can someone explain why Njune 2011 6d i has given the reacting ratio of Mno4 to C2O4 ^2- as 3:5 when the equations balance to give a 2:5 ratio and also the textbook gives it in a 2:5 raito :P the mark scheme couldnt be wrong could it?

Also this thread is kinda dead considering how close to the exam it is :P

There is no ratio needed to be found in question 6d in June 2011, are you sure you sure you got the correct question?

Reply 827

itssochaotic

Original post by Dalts

There is no ratio needed to be found in question 6d in June 2011, are you sure you sure you got the correct question?

revision is seriously getting to me, I meant June 2012. And thanks for looking it up, I kinda worked it out..you gotta combine the two oxidation half equations...

Reply 828

itssochaotic

okay question 6b on January 2011.
The product of Al3+ hexa aqua ion with excesss NaOH is given as Al(OH)6 ^3- in the markscheme-.....From the textbook I have learnt that Al(OH)4^- is always formed...so dont really understand they MS has given that answer. any help would be hellaaa appreciated :biggrin:

Reply 829

SuperFantasticB

The Nelson Thornes textbook says [Co(NH3)6]2+ is yellow-brown and [Co(NH3)6]3+ is yellow.

Q8 (a) (June 2012) says that [Co(NH3)6]2+ is pale yellow and [Co(NH3)6]3+ is dark brown.

I'm really confused. Which is it?

Reply 830

Dirtybit

20

Original post by SuperFantasticB

The Nelson Thornes textbook says [Co(NH3)6]2+ is yellow-brown and [Co(NH3)6]3+ is yellow.

Q8 (a) (June 2012) says that [Co(NH3)6]2+ is pale yellow and [Co(NH3)6]3+ is dark brown.

I'm really confused. Which is it?

Accepted answers I know are: [Co(NH3)6]2+ is Pale brown and [ Co(NH3)6 ] 3+ is Dark Brown

Reply 831

SuperFantasticB

Original post by Dirtybit

Accepted answers I know are: [Co(NH3)6]2+ is Pale brown and [ Co(NH3)6 ] 3+ is Dark Brown

I know [Co(NH3)6]2+ can be accepted as yellow-brown and straw, but why is [Co(NH3)6]3+ yellow in the text book when it's dark brown in the mark scheme? Should I learn it as dark brown then and assume the text book is wrong?

Reply 832

elliewoodheadx

Does anybody have a copy of of the jan13 exam paper for this exam please? :biggrin:

Reply 833

candyhearts

Original post by Mathletic

Do the questions in the nelson thornes / cgp revision guide if you have them and then go through all past papers and pull out periodicity questions and answer them, do this again a few nights before the exam too and im sure youl get an easy 9 marks or so :smile:

Thank you, ha I do hope so

Reply 834

erniiee

13

Original post by Dirtybit

Accepted answers I know are: [Co(NH3)6]2+ is Pale brown and [ Co(NH3)6 ] 3+ is Dark Brown

Original post by SuperFantasticB

I know [Co(NH3)6]2+ can be accepted as yellow-brown and straw, but why is [Co(NH3)6]3+ yellow in the text book when it's dark brown in the mark scheme? Should I learn it as dark brown then and assume the text book is wrong?

The textbook is technically correct, because the hexaamminecobalt(III) ion is yellow, but in solution it appears dark brown due to the presence of other cobalt(III) species. So, a solution would appear dark brown. This is kind of like the discrepancy around chromium(III) and iron(III).

So only write yellow if the question strictly says what is the specific actual colour of it (which it probably wouldn't aha). Otherwise, assume it's referring to a solution, which appears dark brown.

Hope this helps!

Reply 835

Beth_L_G

10

DO we need to know the colours that the p3 oxides burn as?
If so can someone list them, they're arent in my book but were in the book I was using when in year 13 :/

Reply 836

JSN

help?
A solution of hydrogen peroxide of volume 25 cm3 was diluted to 500 cm3. A 25.0 cm3 portion of the diluted solution was acidified and titrated against 0.0150 moldm-3 potassium permanganate solution, and 45.7 cm3 were required. Calculate the concentration of the original hydrogen peroxide solution before dilution, given that hydrogen peroxide is oxidized according to the following equation:
H2O2(aq) → 2H+(aq) + O2(g) + 2e

Reply 837

flyylikejetz

11

Original post by JSN

help?
A solution of hydrogen peroxide of volume 25 cm3 was diluted to 500 cm3. A 25.0 cm3 portion of the diluted solution was acidified and titrated against 0.0150 moldm-3 potassium permanganate solution, and 45.7 cm3 were required. Calculate the concentration of the original hydrogen peroxide solution before dilution, given that hydrogen peroxide is oxidized according to the following equation:
H2O2(aq) → 2H+(aq) + O2(g) + 2e

Find the equation of KMnO4
Find the ratios
Find conc of KMnO4 in 25cm
Find conc of KMnO4 in 500cm
Find moles of hydrogen peroxide using stoichiometric ratio
Divide the moles by 25cm to get the conc.

Reply 838

Dirtybit

20

Original post by SuperFantasticB

I know [Co(NH3)6]2+ can be accepted as yellow-brown and straw, but why is [Co(NH3)6]3+ yellow in the text book when it's dark brown in the mark scheme? Should I learn it as dark brown then and assume the text book is wrong?

The text book is right are somebody said before, but yeah the mark scheme are picky and i suggest you learn what they want! :wink:

Reply 839

JSN

Original post by flyylikejetz

Find the equation of KMnO4
Find the ratios
Find conc of KMnO4 in 25cm
Find conc of KMnO4 in 500cm
Find moles of hydrogen peroxide using stoichiometric ratio
Divide the moles by 25cm to get the conc.

thanks mate, i always get confused when finding conc when going from 25cm3 to 500cm3 why would it be different i always thought that conc will be the same??

AQA CHEM5 A2 Chemistry - 19th June 2013

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