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

1. Can someone explain to me why in the January 2012 paper Question 1e IV you multiply by 1000 instead of dividing by 1000.

http://www.ocr.org.uk/Images/79340-q...-resources.pdf

Thanks!!
2. (Original post by Celestial*Robbie)
Can someone explain to me why in the January 2012 paper Question 1e IV you multiply by 1000 instead of dividing by 1000.

http://www.ocr.org.uk/Images/79340-q...-resources.pdf

Thanks!!
You are working out concentration in mol dm^-3 and you given volume in cm3
3. (Original post by Celestial*Robbie)
Can someone explain to me why in the January 2012 paper Question 1e IV you multiply by 1000 instead of dividing by 1000.

http://www.ocr.org.uk/Images/79340-q...-resources.pdf

Thanks!!
Not sure where you got that you have to multiply by 1000?

Remember concentration, is no. of moles/volume, the volume has to be in dm3, so you have to convert 20.0cm3 of sulfuric acid by dividing it by 1000.
4. (Original post by Celestial*Robbie)
Can someone explain to me why in the January 2012 paper Question 1e IV you multiply by 1000 instead of dividing by 1000.

http://www.ocr.org.uk/Images/79340-q...-resources.pdf

Thanks!!
I got confused on the same question and even after reading peoples responses I'm not sure why the mark scheme says that

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5. (Original post by Celestial*Robbie)
Can someone explain to me why in the January 2012 paper Question 1e IV you multiply by 1000 instead of dividing by 1000.

http://www.ocr.org.uk/Images/79340-q...-resources.pdf

Thanks!!
Because dividing iii by (20/1000) is the same as dividing iii by literally just 20, and then your answer to that times a thousand. That's the method(s) with all them type of questions, or is there something specific you don't understand?
6. (Original post by Willszz1)
Because dividing iii by (20/1000) is the same as dividing iii by literally just 20, and then your answer to that times a thousand. That's the method(s) with all them type of questions, or is there something specific you don't understand?

Ahhh, now I understand!!! I was thinking i had to divide by 20 then divide again by 1000. Thanks! Fully makes sense now!
7. Could someone please make list (or link me to it if its been mentioned already) for the reagents and conditions needed for different reactions, i seem to be losing lots of marks on these questions in past papers.
Thanks
8. (Original post by YA BISH)
Could someone please make list (or link me to it if its been mentioned already) for the reagents and conditions needed for different reactions, i seem to be losing lots of marks on these questions in past papers.
Thanks
If you find this could you message it to me or whatever you do on TSR thanks
9. Could somebody explain what the formula of Sodium nitrate(III) is and how you got to it?

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10. Reagents and conditions[1].pdf

Reagents and conditions list

I think the user 'super121' posted these originally on a similar thread. I'm not sure if these will come out properly, but here goes nothing
11. (Original post by eddyf)
If you find this could you message it to me or whatever you do on TSR thanks
It's up now
12. (Original post by booooomblastruin)
Reagents and conditions[1].pdf

Reagents and conditions list

I think the user 'super121' posted these originally on a similar thread. I'm not sure if these will come out properly, but here goes nothing
thank you very much
13. (Original post by YA BISH)
Could someone please make list (or link me to it if its been mentioned already) for the reagents and conditions needed for different reactions, i seem to be losing lots of marks on these questions in past papers.
Thanks
It's up now
14. can anyone draw a dot and cross diagram of N20?
15. You're welcome! Full credit should go to 'super121'. I was in the same position as you were until he posted this
16. (Original post by Branny101)
Could somebody explain what the formula of Sodium nitrate(III) is and how you got to it?

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NaNO2

This is because the Nitrate (III) has an overall charge of -1 and Na has a charge of +1.

(Na+)(NO2-) the charges cancel each other out so it becomes NaNO2.

Edit: It's NO2- and not NO3- because we're told that nitrogen has an oxidation state of +3.
17. (Original post by super121)
NaNO2

This is because the Nitrate (III) has an overall charge of -1 and Na has a charge of +1.

(Na+)(NO2-) the charges cancel each other out so it becomes NaNO2.
Thaanks

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18. Do we need to know all the solubility rules? Which rules must we know?

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19. what does burn under reflux mean?
20. (Original post by super121)
NaNO2

This is because the Nitrate (III) has an overall charge of -1 and Na has a charge of +1.

(Na+)(NO2-) the charges cancel each other out so it becomes NaNO2.
See
http://en.m.wikipedia.org/wiki/Nitrate
o isn't sodium nitrate NaNO3

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