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# OCR B (Salters) F332 Tuesday 4th June 2013 Exam Discussion (Now Closed) watch

1. (Original post by krisshP)
See
http://en.m.wikipedia.org/wiki/Nitrate
o isn't sodium nitrate NaNO3
No, because the question asks about the formula of Sodium Nitrate(III), telling us that nitrogen has an oxidation state of +3. If it was NO3-, the nitrogen would have an oxidation state of +5, so it has to be NO2-.
2. (Original post by super121)
No, because the question asks about the formula of Sodium Nitrate(III), telling us that nitrogen has an oxidation state of +3. If it was NO3-, the nitrogen would have an oxidation state of +5, so it has to be NO2-.
http://en.m.wikipedia.org/wiki/Nitrate
In NaNO2 the charges cancel out, making sense. It's called sodium nitrate(III) though. But wikipedia says that nitrate=NO3. So how is NaNO2 called sodium nitrate(III)? Shouldn't NaNO2 be called sodium nitrogen dioxide?
3. (Original post by krisshP)
http://en.m.wikipedia.org/wiki/Nitrate
In NaNO2 the charges cancel out, making sense. It's called sodium nitrate(III) though. But wikipedia says that nitrate=NO3. So how is NaNO2 called sodium nitrate(III)? Shouldn't NaNO2 be called sodium nitrogen dioxide?
Nitrate (V) is NO3-, and Nitrate (III) is NO2-.
4. (Original post by Celestial*Robbie)
Ahhh, now I understand!!! I was thinking i had to divide by 20 then divide again by 1000. Thanks! Fully makes sense now!
(Original post by Celestial*Robbie)
Ahhh, now I understand!!! I was thinking i had to divide by 20 then divide again by 1000. Thanks! Fully makes sense now!
Haha no problem
5. guys how do you do jan 10 question 3aii?
6. (Original post by Welbeck)
guys how do you do jan 10 question 3aii?
You know that one of the monomers in the co-polymer is but-2-ene, so find that in the structure of the polymer diagram they give you, You'll see that it's repeated. That'll leave you with the structure of the other monomer, and then it should be clear what it is.
7. How would you explain why ozone has a bond angle of 117°? It has a dative bond and a double bond as well as a lone pair which is putting me off when describing it!
Thankss

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8. Are these correct exam definitions:

Electrophile is positively charged and bonds by accepting a pair of electrons

Nucleophile is negatively charged and has a lone pair of electrons which can be donated to form a covalent bond.
9. (Original post by krisshP)
Are these correct exam definitions:

Electrophile is positively charged and bonds by accepting a pair of electrons

Nucleophile is negatively charged and has a lone pair of electrons which can be donated to form a covalent bond.

I always make sure to say that an electrophile is a positively charged species that is attracted to areas of high electron density, and can form a covalent bond by accepting a lone pair of electrons
10. (Original post by AGKhan)
How would you explain why ozone has a bond angle of 117°? It has a dative bond and a double bond as well as a lone pair which is putting me off when describing it!
Thankss

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Dunno what dative bond you are on about.

Around central O atom there are 3 areas of electron density which repel one another s far apart as possible. Hence ozone has a V shape with a bond angle 118.5*.

120-2.5*=118.5* due to 1 lone pair squeezing bond angle by 2.5* per lone pair.
11. Could some kind person please explain the mark scheme for June 2011, question 4 (d) (i) to me? In the question it asks how to turn methanol into chloromethane. I thought that to turn an alcohol into a chloroalkane that you shake with conc HCl at room temp. However the mark scheme says it is HCl and heat/high temp. I really don't understand where they got that from
12. (Original post by Jlane5000)
I always make sure to say that an electrophile is a positively charged species that is attracted to areas of high electron density, and can form a covalent bond by accepting a lone pair of electrons
But I don't think it says that in the mark schemes. Sorry, it's just that I want to be concise to save precious exam time.
13. (Original post by Jlane5000)
I always make sure to say that an electrophile is a positively charged species that is attracted to areas of high electron density, and can form a covalent bond by accepting a lone pair of electrons
Yeah you are right. It says on Wikipedia attracted to an electron rich centre. It would be good to say it to be on the safe side.

Thanks
14. (Original post by krisshP)
Yeah you are right. It says on Wikipedia attracted to an electron rich centre. It would be good to say it to be on the safe side.

Thanks
No worries, and it does come up in some of the mark schemes, otherwise i wouldn't put it down myself
15. (Original post by krisshP)
Dunno what dative bond you are on about.

Around central O atom there are 3 areas of electron density which repel one another s far apart as possible. Hence ozone has a V shape with a bond angle 118.5*.

120-2.5*=118.5* due to 1 lone pair squeezing bond angle by 2.5* per lone pair.
Presumably the mark scheme would allow 120*, as that is what we are taught for 3 areas of electron density without looking it up on line?
16. (Original post by King Hotpie)
Presumably the mark scheme would allow 120*, as that is what we are taught for 3 areas of electron density without looking it up on line?
This is what i'd've thought, one double-bond, one dative and one lone is what we were taught?

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17. (Original post by Jlane5000)
No worries, and it does come up in some of the mark schemes, otherwise i wouldn't put it down myself
The mark schemes are so weird. Like mostly they accept saying high frequency UV, then there's one where they only accept high energy UV
18. (Original post by krisshP)
The mark schemes are so weird. Like mostly they accept saying high frequency UV, then there's one where they only accept high energy UV
I know I hate how they can just change their minds each year so definitely best to cover all your bases, put it down even if its only been in a few of the mark schemes
19. Do you need to remember planck's constant?
20. (u) describe in outline the preparation of a chloroalkane from
an alcohol using HCl:

What is this specifically asking for? It's probably something simple but I've never seen something that asks for the preparation of chloroalkane etc

Is it just like ch3cl+ h20 -> ch3oh+ hcl? Or something else

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