ocr a f325 revision thread

Reply 2000

115 isn't bad! I need about 83% if I didn't go up in my F321 retake, but I genuinely have no idea how it went because it's so much easier than A2 I feel like I have nothing to gage it on! Good luck! If you need any more help ask me because I need the practice!!

Ah I see, I know what you mean.. i resat F321 in January and went from 69/90 to 86/90 it is not even comparable to what we're going to face on Wednesday is it!
Thank you :smile:

I will :P

Reply 2001

otrivine

14

An unusual compound of iron has been detected on the surface of the planet Mars. This compound contains the ferrate(VI) ion.
A student uses 1.00 g of iron(III) oxide and makes, on crystallisation, 0.450 g of sodium ferrate(VI), Na2FeO4.
Calculate the percentage yield, by mass, of sodium ferrate(VI).

how did they get the mass of Sodium ferrate as 2.08g ? thanks

Reply 2002

Theafricanlegend

15

anyone here got jan 13 ms

Reply 2003

Namod

10

Original post by needtosucceed=)

no idea im afraid :/ in the specification it states only for monoprotic acids :/
it seems like a reasonable thing to do if it does come up :smile:

You got the first post of page 100
Lucky.

Reply 2004

überambitious_ox

14

Original post by bmpink

115 isn't bad! I need about 83% if I didn't go up in my F321 retake, but I genuinely have no idea how it went because it's so much easier than A2 I feel like I have nothing to gage it on! Good luck! If you need any more help ask me because I need the practice!!

bmpink, please could you help me with a question that I have posted on the previous page (I think or page before)?

Reply 2005

F Hopeful

Original post by otrivine

An unusual compound of iron has been detected on the surface of the planet Mars. This compound contains the ferrate(VI) ion.
A student uses 1.00 g of iron(III) oxide and makes, on crystallisation, 0.450 g of sodium ferrate(VI), Na2FeO4.
Calculate the percentage yield, by mass, of sodium ferrate(VI).

how did they get the mass of Sodium ferrate as 2.08g ? thanks

Fe2O3 > 2NaFeO4

so you find the moles of Fe2O3, multiply by 2 for the moles of NaFeO4 then multiply by Mr for the mass

Reply 2006

_HabibaH_

8

Original post by otrivine

they put 1 ?

Yes that makes sense actually. 1 mole to 1 mole. Stoichiometry is equal.

Reply 2007

otrivine

14

Original post by F Hopeful

Fe2O3 > 2NaFeO4

so you find the moles of Fe2O3, multiply by 2 for the moles of NaFeO4 then multiply by Mr for the mass

can you show me please

Reply 2008

otrivine

14

Original post by _HabibaH_

Yes that makes sense actually. 1 mole to 1 mole. Stoichiometry is equal.

is it because of the mole ratio

Reply 2009

F Hopeful

Original post by otrivine

can you show me please

you find the Mr of Fe in Fe2O3 which is 159.6

n(Fe2O3) = mass/mr

1/159.6= 0.006266 mol

what I did then was set up an equation for the reaction so

Fe2O3 + 4Na + 5H2O----> 2Na2FeO4 + 5H2

the ratio of Fe2O3 to Na2FeO4 is 1:2 so moles of Na2FeO4 = 2x0.006266 = 0.012532

mass of Na2FeO3= moles x mr = 0.012532x165.8= 2.08g

:smile:

Reply 2010

_HabibaH_

8

Original post by otrivine

is it because of the mole ratio

Yep. Is there anything you found hard cuz you know A LOT so anything you think is worth looking at, would help everyone I think.

Reply 2011

needtosucceed=)

10

Original post by Namod

You got the first post of page 100
Lucky.

OMG really.
i'm a don :')

Reply 2012

Tidius

Hey all just a small question, when drawing out complex ions in 3d form whats the best way to show it being a dative bond without it looking messy?
because i see that they sometimes dont even draw arrows showing its dative?

Cheers

Reply 2013

otrivine

14

Original post by _HabibaH_

Yep. Is there anything you found hard cuz you know A LOT so anything you think is worth looking at, would help everyone I think.

Sorry I just keep getting panicked when exam is getting closer :tongue:

Reply 2014

_HabibaH_

8

Original post by otrivine

Sorry I just keep getting panicked when exam is getting closer :tongue:

Same lol. When I'm not panicking, i'm wasting time thinking of how much I'm panicking.

Reply 2015

Pafeetus

11

Original post by Tidius

Hey all just a small question, when drawing out complex ions in 3d form whats the best way to show it being a dative bond without it looking messy?
because i see that they sometimes dont even draw arrows showing its dative?

Cheers

You don't need to show it's dative, just make sure it's 3D structure is clear.

Posted from TSR Mobile

Reply 2016

mmasters

Quick question, do we have to cover Kp?

Reply 2017

otrivine

14

The cell represented below was set up under standard conditions.
Pt|Fe2+(aq), Fe3+(aq)||Tl3+(aq),Tl+(aq)|Pt Cell e.m.f. = + 0.48 V
(i) Deduce the standard electrode potential for the following half-reaction.
Tl3+(aq) + 2e– → Tl+(aq)
...........................................................................................................................

how?

Reply 2018

mmasters

Also when calculating entropy ^S and there are two moles of either a reactant or product as a pose to one, do we then times the number in the table by two, or not?