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OCR Salters Chemistry F335 12th June 2013 Exam revision thread

Reply 740

DoeADeer

9

What do people think the grade boundaries will be??

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Reply 741

C.JTop

5

Original post by autodidactmedic

Ditto. Do you think if I stated pd-pd as an interaction between the hydrocarbon chains that I'll lose a mark?

yeah maybe, they both would have the same strength of pd-pd forces i think, so that wouldn't be a factor

Reply 742

Mattywooda

Original post by chemistryfailure

I put 2HCOOH + CaCO3 = CO2 + H2O + CA(OH)2 ...... is that wrong?

I think it should be:

2HCOOH + CaCO3 ==> CO2 + H20 + Ca(HCOO)2

Reply 743

autodidactmedic

Original post by Reina

I didn't know whether to write about ligands since I think it said "transition metal compounds" rather than "complexes".

My answer was "Electrons absorb light energy and move to higher energy levels. The frequency absorbed depends on the energy gap between two energy levels (deltaE = hv). The complimentary colour is reflected or transmitted."

It didn't feel like enough, but the question was 5 marks - one being QWC :s-smilie:

I know, if they meant we should describe ligands then that is not your fault as they should have made it clearer. I bet in the right hand column of the mark scheme it will say "emit = CON." Damn you OCR

Reply 744

calmpeach

7

how did people answer the acid question where it said half of the acid had reacted with sufficient amounts of NaOH??

Reply 745

C.JTop

5

Original post by AmirHabeeb

Oxidation/Reduction involve a change in number of electrons. There was no change. I think it's elimination. :colondollar:

oh i see what you mean now :frown:

Reply 746

JG17

I wrote that too. I'm fairly sure it was as I think you had to work backwards from the second equation, where the hydrogen ions increased so the POE shifted to the products and that shifted the POE on the first equation to the left?

Reply 747

autodidactmedic

Original post by C.JTop

yeah maybe, they both would have the same strength of pd-pd forces i think, so that wouldn't be a factor

Reply 748

C.JTop

5

Original post by Mattywooda

prove Ka = 1.7E-4, when pH is 3.77.

Then pH when HA = A-, 3.77.

pH when half acid has reacted with NaOH, pH = 4.07

i got that too :biggrin:

Reply 749

suncake

14

Original post by JG17

I wrote that too. I'm fairly sure it was as I think you had to work backwards from the second equation, where the hydrogen ions increased so the POE shifted to the products and that shifted the POE on the first equation to the left?

That's incorrect - look at Chemical Storylines page 139.

That silly book does come in handy occasionally!

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Reply 750

NiceToMeetYou

1

Ohhhhhhhh OCR, Why you so mean to us? :frown:

Reply 751

ells-13

+5 Antimony (V) oxide

Reply 752

super121

5

Original post by ells-13

+5 Antimony (V) oxide

I got that :smile:

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Reply 753

autodidactmedic

Original post by ells-13

+5 Antimony (V) oxide

YES!

Reply 754

Narwhaleninja

Anybody know what kind of raw marks is 100 % UMS?

Reply 755

Sujman

1

Original post by autodidactmedic

yes!

yeeeeeeeeeeeeeeessssssssssssssssss

Reply 756

tntech

I put acid-base reaction for the one where H+ is lost, as they react with NaOH and a hydrogen is donated to the base and lost? I thought it was elimination first but if a hydrogen goes missing when it reacts with a strong base like NaOH I assumed acid-base reaction...