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OCR Salters Chemistry F335 12th June 2013 Exam revision thread

Reply 80

abzy1234

14

Original post by nukethemaly

Heres a clean F335 Jan 2013 paper if anyone needs it

Thanks a lot! :biggrin:

Reply 81

Salmonidae

1

Quick question, 2. d) in F335 June 2010 which is here.

I understand the molecules not getting as close in t-butanol and that this would cause weaker intermolecular bonds, but I'm confused as to why they would both show instantaneous dipole-instantaneous dipole bonding and not hydrogen bonding, they both have alcohol groups. I'm obviously getting something muddled, any help would be appreciated!

Thanks!

Reply 82

Reyoru

1

Original post by Salmonidae

Quick question, 2. d) in F335 June 2010 which is here.

I understand the molecules not getting as close in t-butanol and that this would cause weaker intermolecular bonds, but I'm confused as to why they would both show instantaneous dipole-instantaneous dipole bonding and not hydrogen bonding, they both have alcohol groups. I'm obviously getting something muddled, any help would be appreciated!

Thanks!

They both have the ability to form two hydrogen bonds (two lones pairs on each oxygen) per molecule so talking about hydrogen bond strength seems redundant in this case. All compounds exhibit ID-ID (some experience additional bonding on top of this) and one compound is more branched so it makes more sense to talk about ID-ID forces here.

(edited 10 years ago)

Reply 83

thelion0

11

How is everyone revising?

Reply 84

abzy1234

14

Original post by Salmonidae

Quick question, 2. d) in F335 June 2010 which is here.

I understand the molecules not getting as close in t-butanol and that this would cause weaker intermolecular bonds, but I'm confused as to why they would both show instantaneous dipole-instantaneous dipole bonding and not hydrogen bonding, they both have alcohol groups. I'm obviously getting something muddled, any help would be appreciated!

Thanks!

I think it's mainly due to the fact that the large alkyl groups disrupt the nature of the hydrogen bonding. Because more groups can form idid bonds, hydrogen bonds will not be as effectual.

Whereas if you have a smaller molecule like ethanol, there's only one alkyl group, so it won't disturb the hydrogen bonding in a carboxylic acid.

Hope that makes a bit more sense! :smile:

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Reply 85

hannahhannah1

Hey guys, can someone help me on this question?

Thallium(I) bromide is insoluble in water. The main reason for this is the small size of the
negative hydration enthalpy of the Tl + ion. Give two reasons why this value is small.

Why is the charge density small? I thought larger the charge, smaller the charge density?

Reply 86

Reyoru

1

Original post by hannahhannah1

Hey guys, can someone help me on this question?

Thallium(I) bromide is insoluble in water. The main reason for this is the small size of the
negative hydration enthalpy of the Tl + ion. Give two reasons why this value is small.

Why is the charge density small? I thought larger the charge, smaller the charge density?

Charge density is a combination of the charge on the ion as well as its size. It has a +1 charge which is quite small anyways but also if you look at its location in the periodic table, it has many electron sub-shells so it's a large ion. This means that in any unit volume, there are lots of these thalium ions so the charge density is small as total charge per unit volume is small. Hope that helped. :smile:

Reply 87

Pandora's Box

Hi, does anyone happen to have the mark scheme for the F334 January 2013 paper? I can't find it anywhere..

Thanks!

Reply 88

nukethemaly

11

Original post by Pandora's Box

Hi, does anyone happen to have the mark scheme for the F334 January 2013 paper? I can't find it anywhere..

Thanks!

Here!

I've also attached the paper in case anyone needs it!

2013_F334_January.pdf352.9KB

2013_Markscheme_January_F334.pdf97.4KB

Reply 89

Pandora's Box

Original post by nukethemaly

Here!

I've also attached the paper in case anyone needs it!

Brilliant! Thankyou! :biggrin:

Reply 90

josephtsui

How's everyone preparing for F335? I'm finding it much harder than all the other modules. I'm thinking about redoing some of the F334 papers for practice as most of the F335 papers are synoptics.

Reply 91

nukethemaly

11

Original post by suncake

Nope, we're halfway through Oceans, and starting Medicines by Design after Easter. Saying that, I did my first past paper today and it literally seemed like most of it was just synoptic from either AS or earlier in A2, with only 1 or 2 things we hadn't covered yet. Not sure whether that's a good or bad thing..!

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As you keep doing the papers, you'll realise that it's all very repetitive and feel even better about it all!

Reply 92

abzy1234

14

Original post by josephtsui

How's everyone preparing for F335? I'm finding it much harder than all the other modules. I'm thinking about redoing some of the F334 papers for practice as most of the F335 papers are synoptics.

Past papers for sure, you'll get used to how they will ask you, especially in the weird style of "synopticity". I'm kind of lucky (in a sense!) that I'm also doing F332 and F334, so most of prior learning I can slot into F335; but I would recommend reading all your notes from F331 to F334, and doing some past paper questions again.

You need to have all bases covered for this exam :smile:

Reply 93

Tikara

Does anyone know if NaBH4 reduces carboxylic acids to aldehydes?? It just seems logical as it reduces aldehydes and ketones

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Reply 94

ActaNonVerba

has electrode potential ever shown its face in this exam!? that would be just uncalled for

Reply 95

ActaNonVerba

Original post by Tikara

Does anyone know if NaBH4 reduces carboxylic acids to aldehydes?? It just seems logical as it reduces aldehydes and ketones

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The acidity would decompose the borohydride before its reducing power can be utilized.

Reply 96

calmpeach

7

Original post by ActaNonVerba

has electrode potential ever shown its face in this exam!? that would be just uncalled for

Nope it's not come up yet! And I doubt it will because its not in the spec!
I recommend reading the spec because it tells you exactly what you'll need to know and what might come up in the exam! :smile: