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OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012

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hey anyone wants to revise tomorrow chapter 1> ?
Original post by otrivine
hey anyone wants to revise tomorrow chapter 1> ?


Yeah why not? :smile:
Original post by LifeIsGood
Yeah why not? :smile:


shall we do some now?
Ok
ill start
Define:strong acid and give an example (3)
Original post by otrivine
shall we do some now?
Ok
ill start
Define:strong acid and give an example (3)


A strong acid is an acid which completely dissociates.
Example: HCl
HCl --> H+ + Cl-
Reply 204
Avatar for Silkyy
Silkyy
Does anybody know how you know when you need to X1000 or divide by 1000 in the 'Free energy change' calculations? In some questions it asks you to put entropy of reaction in J and others in KJ so i'm not sure which to do :s-smilie:
Reply 205
Avatar for Killjoy-
Killjoy-
8
Original post by Silkyy
Does anybody know how you know when you need to X1000 or divide by 1000 in the 'Free energy change' calculations? In some questions it asks you to put entropy of reaction in J and others in KJ so i'm not sure which to do :s-smilie:


Converting from kJ to J: multiply by 1000
Converting from J to kJ: divide by 1000

Think about it this way - there are 1000J in one kJ.

Oh and as long as you are consistent with your units you should get the same answer; if you are specifically asked to change to a particular unit then do so.
(edited 11 years ago)
Original post by LifeIsGood
A strong acid is an acid which completely dissociates.
Example: HCl
HCl --> H+ + Cl-


yes excellent my turn
Reply 207
Avatar for Silkyy
Silkyy
So should i always convert it into KJ or J?
Original post by Silkyy
So should i always convert it into KJ or J?


hi can we ask questions on chapter 1?
Reply 209
Avatar for Killjoy-
Killjoy-
8
Original post by Silkyy
So should i always convert it into KJ or J?


All quantities must have the same prefix, so either all in kilo or all without kilo.
Reply 210
Avatar for Killjoy-
Killjoy-
8
Original post by otrivine
hi can we ask questions on chapter 1?


I'm afraid that I can't - I'm doing FP3 at the moment. :smile:
Original post by Killjoy-
I'm afraid that I can't - I'm doing FP3 at the moment. :smile:


10 min only :wink: :wink: please only on chap 1
Reply 212
Avatar for kingam
kingam
Original post by otrivine
yes excellent my turn


You Can ask me
If you want
Original post by kingam
You Can ask me
If you want


sure but you start :wink: chap 1
Reply 214
Avatar for kingam
kingam
Original post by otrivine
sure but you start :wink: chap 1


Erm , how do work out the ph of a strong base
Original post by kingam
Erm , how do work out the ph of a strong base


by doing titration and using a PH meter to see how strong the base is from PH 8-14 AND there is a formula to find PH which is PH=-Log(H+)
Reply 216
Avatar for kingam
kingam
Original post by otrivine
by doing titration and using a PH meter to see how strong the base is from PH 8-14 AND there is a formula to find PH which is PH=-Log(H+)

Erm not really you subtract 14 from - log oh value .
Original post by kingam
Erm not really you subtract 14 from - log oh value .


oh so would i get no marks?
ok
how can you check change colour (2)
Reply 218
Avatar for kingam
kingam
Original post by otrivine
oh so would i get no marks?
ok
how can you check change colour (2)


Your probably wouldn't as they are like calculation questions , and colour change you choose an indicator and one colour appears in its conjugate base and acid , for eg methyl orange can change from red to yellow , is that t question was a
Bit vague lol
Original post by kingam
Your probably wouldn't as they are like calculation questions , and colour change you choose an indicator and one colour appears in its conjugate base and acid , for eg methyl orange can change from red to yellow , is that t question was a
Bit vague lol


No you would do a precepitation reaction
but yes you seem to get the point
ok my turn

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