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OCR Chemistry F321 Exam. - [Next Tuesday[

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Reply 160

RandomMedic

Original post by TheFootyKing19

Holz88 - they gave one of the products for the concentrated Naoh equation. Read the question agian :smile:

Original post by JuxtaposedJames

If I remember correctly that involved NaClO3

All they were testing is your knowledge then application of oxidation numbers

There are usually one/two a* questions in which are slightly off spec and require you to apply your knowledge of chemistry rather than just remember it. However they always give you all the information you need, there is never anything that you wouldn't be able to answer.

Original post by Pride

oh I remember that one.

our chem teacher just told us to write down an extra one in our notes. It's not particularly fair is it. Well they do worse things in biology exams

Ah I see, yeah. I wondered why I got it wrong, because I got the right products, but just careless balancing I suppose.
Yeah, they can be pretty cruel in biology. Numerous times I've seen questions that I hadn't learnt until the next module in past papers. That happened once in chem and my teacher was red in the face when she explained about it :L

Reply 161

otrivine

is the reasoning for group 2 and 7 down the group the same like increase atomic radius and shielidng thing

Reply 162

EmilyBea

does anyone know how you work out Q1 e v on the june 2011 paper?! havent got a clue

http://www.ocr.org.uk/download/pp_11_jun/ocr_66603_pp_11_jun_gce_uf321.pdf

Reply 163

Craming Revision

Original post by Pride

yeah sorry, I'll stop asking that question now haha

mate i need help with bond angles? ://// lol like shapes like h2o2 n2h2 just incase any random thing with 2 molecules come up im lost on that lol x

Reply 164

Paktriot

Original post by emilyannea

does anyone have the f321 for jan 2012?

I have the hard copy?

Reply 165

Paktriot

Original post by EmilyBea

does anyone know how you work out Q1 e v on the june 2011 paper?! havent got a clue

http://www.ocr.org.uk/download/pp_11_jun/ocr_66603_pp_11_jun_gce_uf321.pdf

You look for the jump, which is after the first 2 energies.
You know that those two are the outer shell electrons because they require less
energy to be pulled off.

So now you know that its in Group 2. In the question they ask about the first 18 elements only. So it must be Mg as Be's electrons are too less and 6 ionization energies are shown.

Reply 166

eemooz

Original post by JoeLatics

Are any of you guys Y13 resitters? Genuinely can't believe how much easier AS seems having done A2, so chins up guys :-)

Me haha! I'm doing my whole chemistry a level. FML. :frown:

Reply 167

Joey952

in jan 2012 it asked the bond angle for H-N-H , could some one tell me the answer and why please ?

Reply 168

eemooz

Original post by otrivine

Thanks for telling me i will be aware of that :wink:

ok
1)How would you carry out a acid-base titration(3)
2) What colour does methylorange give in acid?

Titrations?! Since when did we need to know this?
Kill me now :frown:

Reply 169

Pride

Original post by Craming Revision

mate i need help with bond angles? ://// lol like shapes like h2o2 n2h2 just incase any random thing with 2 molecules come up im lost on that lol x

I've had a look on wiki for peroxide, it's unlikely to come up. It's not a normal molecule that abides by the rules we've learnt.

You can do it.

with hydrazine, N2H4 there are 2 N atoms, acting as central atoms, and 2 hydrogen atoms around each. So around each N atom is 3 bonded pairs and a lone pair. Draw it if you like, that's what I did in that test. So what would the bond angle be? 109.5 - 2.5 = 107. Then you would explain why, talk about how the regions of electron density repel each other as far as possible around the central N atom, trigonal pyramidal shape around both N atoms.

Original post by Joey952

in jan 2012 it asked the bond angle for H-N-H , could some one tell me the answer and why please ?

here you go, it's just like NH3 on either side.

(edited 11 years ago)

Reply 170

Paktriot

Original post by Joey952

in jan 2012 it asked the bond angle for H-N-H , could some one tell me the answer and why please ?

It was the NH2 bond angle in 2H-N-N-H2

The bond angle is 107 because there are 3 bonded pairs and one lone pair.

Reply 171

eemooz

Original post by Joey952

in jan 2012 it asked the bond angle for H-N-H , could some one tell me the answer and why please ?

The answer is 104.5 because there's two bonded pairs and two lone pairs.

Now you're probably thinking two lone pairs? N only has five electrons...
But when it has reacted with hydrogen it becomes (NH2)- so it has an extra electron, which completes the second line pair :smile:

Actually just read the above post, I didn't know it was part of a molecule, so the above post is correct

TSR= the only place you get begged for actually trying to help lol.

(edited 11 years ago)

Reply 172

otrivine

Original post by eemooz

Titrations?! Since when did we need to know this?
Kill me now :frown:

its in the book dont be silly i am sure u will be fine! just revise it quickly its not long :smile:

Reply 173

supernova99

Original post by AAA_

Does anyone have the paper for F321 jan 2012? It would be much appreciated.

Here you go, the paper and markscheme :smile:

F321-01Jan12 (1).pdf218.2KB

F321_MS_Jan12 (1).pdf196.1KB

Reply 174

Joey952

Original post by AlligatorSky

It was the NH2 bond angle in 2H-N-N-H2

The bond angle is 107 because there are 3 bonded pairs and one lone pair.

That makes sense now

Reply 175

Pride

Original post by EmilyBea

does anyone know how you work out Q1 e v on the june 2011 paper?! havent got a clue

http://www.ocr.org.uk/download/pp_11_jun/ocr_66603_pp_11_jun_gce_uf321.pdf

Yes, apply your knowledge on ionisation energies!

Remember, we can tell what the atom is from where the jump in ionisation energies is. After the 2nd IE, there is a larger jump in IE.

This means the next electron has been taken from a different shell, closer to the nucleus. So which element must it be?