OCR Chemistry B (Salters) Thursday 10th January Discussion

Alright I think... My past papers have varied from 49 to 57, but all above 80%, so with a bit of luck it will go well. How about you?

Reply 101

Tikara

anyone have the f331 past paper from June 2012?

Reply 102

munna07

hows everyone feeling for the exam tomorrow? :smile:

Reply 103

Tikara

Original post by munna07

hows everyone feeling for the exam tomorrow? :smile:

scared, second time resitting - need a B D:

When you draw ionic dot and crosses will you get marked down if you don't put the bonding electron pairs on the wrong sides e.g opposite sides of an atom (S) rather than next to each other

^-- should be called 2minus haha i'm in a rush

I drew the bonding dot and crosses opposite each other, I know it's wrong but would I get penalised??

Reply 104

King Hotpie

15

Original post by Tikara

scared, second time resitting - need a B D:

When you draw ionic dot and crosses will you get marked down if you don't put the bonding electron pairs on the wrong sides e.g opposite sides of an atom (S) rather than next to each other

^-- should be called 2minus haha i'm in a rush

I drew the bonding dot and crosses opposite each other, I know it's wrong but would I get penalised??

I can't guarantee anything but I highly doubt it- remember, the electrons are orbiting the nucleus, we draw simple dot cross diagrams, but in real life it's far more complicated and the electrons certainly don't stay in one place.

Reply 105

Tikara

Original post by Ben Dodds

I can't guarantee anything but I highly doubt it- remember, the electrons are orbiting the nucleus, we draw simple dot cross diagrams, but in real life it's far more complicated and the electrons certainly don't stay in one place.

okay, thanks very much

Does anyone have the June 2012 paper and MS?

OCR are so annoying with their new website all my bookmarks don't work :frown:

Reply 106

Welbeck

3

a bit nervous about this exam, want an A or B but hopefully and A. I am just waiting for the guy to post the mark scheme, i had a look at it today but had to hand it back in

Reply 107

Welbeck

3

Estebank, did you manage to get the mark scheme?

Reply 108

MissEmilyAmber

Hello!

I've just a quick query: If there is a question which 'suggests' you draw a diagram to support your answer, will you get penalized if you do not? I understand that in using the word 'suggest' full marks should still be available for the question regardless of whether or not you do so, however my teacher told me that this isn't always the case. Anybody out there who can clear this up from past experiences?
Many thanks and best of luck to everybody sitting the exam tomorrow. :smile:

Reply 109

RoBiNBolt

Yoooo! Can anyone explain Bond Angles to me?? :smile:

Reply 110

Welbeck

3

Original post by MissEmilyAmber

Hello!

I've just a quick query: If there is a question which 'suggests' you draw a diagram to support your answer, will you get penalized if you do not? I understand that in using the word 'suggest' full marks should still be available for the question regardless of whether or not you do so, however my teacher told me that this isn't always the case. Anybody out there who can clear this up from past experiences?
Many thanks and best of luck to everybody sitting the exam tomorrow. :smile:

It is likely in most cases you would lose a mark, for example in the jan 11 paper question 4bii, they suggest you to draw a diagram (for atomic spectroscopy) and you must have a diagram to get 1 of the marks (to show something) according to the mark scheme

Reply 111

xOsugaplumfairy

I hope I get an A or B :frown:

I've been revising like crazzzyyyy

Reply 112

Bow Tie

14

Original post by RoBiNBolt

Yoooo! Can anyone explain Bond Angles to me?? :smile:

Best way to put it is a central atom surrounded by:
Example: CO, 2 atoms = 180 degrees, Shape: Linear
Example: BF3, 3 atoms = 120 degrees, Shape: Trigonal Planar
Example: CH4, 4 atoms = 109 degrees, Shape: Tetrahedral
Example: PCl5, 5 atoms = 120 degrees and 90 degrees, Shape: Trigonal by-pyramidal
Example: SF6, 6 atoms = 90 degrees, Shape: Octahedral (Counter-intuitive being SIX atoms...)

Ammonia is a strange one, it has a lone pair so it is 109 degrees and is named as 'Pyramidal'
Then finally an example of water which is 'Bent' or 'Boomerang' which has 2 lone pairs and so has a bond angle 109 degrees

Hope that helps, its the best way I find to revise the shapes of molecules. Just remember that its all to do with the 'groups' of electrons NO MATTER how many electrons are in each group so if there are 3 groups made up of 2,2,4 electrons, then the bond angle is still 120 degrees as there are 3 groups of electrons!

If anyone else needs help, I am happy to help if I know! Its good revision for me too!

(edited 11 years ago)

Reply 113

Garyglitter

Any chance of tomorrow's paper being leaked ?

Reply 114

Janoskian

does anyone know how a zeolite works? i know it acts as a sieve to separate branched and unbranched isomers, but which does it allow to pass through?

so confused!

Reply 115

Bow Tie

14

Original post by Janoskian

does anyone know how a zeolite works? i know it acts as a sieve to separate branched and unbranched isomers, but which does it allow to pass through?

so confused!

Zeolite is shaped almost like a donut on a molecular level and so it has a hole through the middle that allows the straight chain isomers to pass through but restricts the passage of the short, branched isomers, thus separating the straight chains from the branched isomers :biggrin:

Zeolite structure:
http://www.co2crc.com.au/images/imagelibrary/cap_diag/zeolites._adsorption_media.jpg
See the hole through the middle?

Reply 116

Sammydodga

A zeolite contains holes that trap the branched isomers and allows the unbranched (straight-chain) isomers to pass through.

Reply 117

momena

A zeolites are heterogeneous catalysts which have a large surface area, it also has pores which stop branched molecules from passing through.

Reply 118

Sammydodga

Original post by Ali_Ludley

Best way to put it is a central atom surrounded by:
Example: CO, 2 atoms = 180 degrees, Shape: Linear
Example: BF3, 3 atoms = 120 degrees, Shape: Trigonal Planar
Example: CH4, 4 atoms = 109 degrees, Shape: Tetrahedral
Example: PCl5, 5 atoms = 120 degrees and 90 degrees, Shape: Trigonal by-pyramidal
Example: SF6, 6 atoms = 90 degrees, Shape: Octahedral (Counter-intuitive being SIX atoms...)

Ammonia is a strange one, it has a lone pair so it is 109 degrees and is named as 'Pyramidal'
Then finally an example of water which is 'Bent' or 'Boomerang' which has 2 lone pairs and so has a bond angle 109 degrees

Hope that helps, its the best way I find to revise the shapes of molecules. Just remember that its all to do with the 'groups' of electrons NO MATTER how many electrons are in each group so if there are 3 groups made up of 2,2,4 electrons, then the bond angle is still 120 degrees as there are 3 groups of electrons!

If anyone else needs help, I am happy to help if I know! Its good revision for me too!

Hey how would you answer a 4 mark question on atomic emission spectra. All I know is E=hv. And if it says draw a diagram what would you draw?
thanks

Reply 119

Janoskian

Thanks!

Original post by Ali_Ludley

Zeolite is shaped almost like a donut on a molecular level and so it has a hole through the middle that allows the straight chain isomers to pass through but restricts the passage of the short, branched isomers, thus separating the straight chains from the branched isomers :biggrin:

Zeolite structure:
http://www.co2crc.com.au/images/imagelibrary/cap_diag/zeolites._adsorption_media.jpg
See the hole through the middle?

haha thankyou!! :smile:

Original post by Sammydodga

A zeolite contains holes that trap the branched isomers and allows the unbranched (straight-chain) isomers to pass through.