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

1. (Original post by Jlane5000)
Hi can someone please help me with this part of the spec "Explain the risks associated with the storage and transport of the halogens (fluorine to iodine)"

I've gone through all past paper mark schemes and can't compile a complete list. I know they are toxic/corrosive and that they should all be kept away from flames, but are there any specific ones for each halogen?

Cheers
Anyone?
2. Fluorine and chlorine are both gases, so they'll spread quickly and be more difficult to clean up? Also more difficult to store. Similar with (liquid) bromine but on a lesser scale.
3. (Original post by King Hotpie)
Fluorine and chlorine are both gases, so they'll spread quickly and be more difficult to clean up? Also more difficult to store. Similar with (liquid) bromine but on a lesser scale.
Thanks
4. (Original post by krisshP)
WTF are you serious? I thought you just split all aqueous reactants into ions? This is so bloody confusing!
Of course the aqueous products split too, or else how would you expect to cancel out the spectator ions that are the same on BOTH sides?
5. (Original post by krisshP)
What do you mean by this?
Say if you have a question that says:
Write an ionic equation for the reaction of barium chloride solution with sodium sulfate solution. A precipitate of barium sulfate forms:

then first step: BaCl2(aq) + Na2SO4(aq) --> BaSO4(s) + 2NaCl (aq)

right?

then next step: split all aqueous products and reactants into its ions:
Ba^2+(aq) + 2Cl^-(aq) + 2Na^+(aq) + SO4^2-(aq) --> BaSO4(s) + 2Na^+ + 2Cl^-

alright, now let me explain why I've put two infront of few of these ions, it's because in the first step you have BaCl2, that means one ion of barium and 2 of chloride, and same for the rest, but for 2NaCl, its two of sodium and 2 of chlorine.

Okay now finally: cancel out the ions that are same on both sides, so your final equation is:
Ba^2+(aq) + SO4^2-(aq) --> BaSO4 (s)
6. (Original post by nukethemaly)
Hey when I speak about rate of reaction etc, does it sound better to say "more collisions per unit of time" or "frequent collisions" because in every mark scheme its a different story!
I prefer to say more frequent collisions. Since f=1/T, where T is the time period, 'per unit time' would probably also be acceptable. So honestly I don't think it matters.
7. (Original post by krisshP)
But I thought you only split aqueous reactants?

This is so confusing ahhhhhhhhh
yes both aqueous reactants and aqueous products, but nothing solid. BECAUSE IF THEY'RE IN A SOLUTION AQUEOUS THINGS ARE BOUND TO DISSOLVE (HENCE SPLIT INTO THEIR IONS BECAUSE THEY'RE HYDRATED NOW) AND THE SOLID WONT. THE SOLID JUST SETTLES DOWN.
8. (Original post by StephenNaulls)
I prefer to say more frequent collisions. Since f=1/T, where T is the time period, 'per unit time' would probably also be acceptable. So honestly I don't think it matters.
Thank you! You're the guy with the signature stuff right? How many do we have now?
9. (Original post by nukethemaly)
Thank you! You're the guy with the signature stuff right? How many do we have now?
I am- this is slightly off topic so if you want to speak about it PM me. But I believe we hit 6,700 last night, which isn't bad for two weeks worth of work.

Good luck with the exam!
10. (Original post by StephenNaulls)
I am- this is slightly off topic so if you want to speak about it PM me. But I believe we hit 6,700 last night, which isn't bad for two weeks worth of work.

Good luck with the exam!
Yay go us!

Thanks, you too
11. (Original post by nukethemaly)
Say if you have a question that says:
Write an ionic equation for the reaction of barium chloride solution with sodium sulfate solution. A precipitate of barium sulfate forms:

then first step: BaCl2(aq) + Na2SO4(aq) --> BaSO4(s) + 2NaCl (aq)

right?

then next step: split all aqueous products and reactants into its ions:
Ba^2+(aq) + 2Cl^-(aq) + 2Na^+(aq) + SO4^2-(aq) --> BaSO4(s) + 2Na^+ + 2Cl^-

alright, now let me explain why I've put two infront of few of these ions, it's because in the first step you have BaCl2, that means one ion of barium and 2 of chloride, and same for the rest, but for 2NaCl, its two of sodium and 2 of chlorine.

Okay now finally: cancel out the ions that are same on both sides, so your final equation is:
Ba^2+(aq) + SO4^2-(aq) --> BaSO4 (s)
Oh i get it now thanks so then how come OCR give you such little working out space for ionic equations? So ridiculous.

Thanks
12. (Original post by nukethemaly)
yes both aqueous reactants and aqueous products, but nothing solid. BECAUSE IF THEY'RE IN A SOLUTION AQUEOUS THINGS ARE BOUND TO DISSOLVE (HENCE SPLIT INTO THEIR IONS BECAUSE THEY'RE HYDRATED NOW) AND THE SOLID WONT. THE SOLID JUST SETTLES DOWN.
What about liquid, gas? Say if you had H2O(l), would you split that into 2H+(l) and O^2-(l) or just leave it?
13. (Original post by krisshP)
What about liquid, gas? Say if you had H2O(l), would you split that into 2H+(l) and O^2-(l) or just leave it?
don't ever split up liquids, gases or solids
14. (Original post by Jlane5000)
don't ever split up liquids, gases or solids
Aaaah only aqueous reactants and products?

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15. (Original post by krisshP)
Oh i get it now thanks so then how come OCR give you such little working out space for ionic equations? So ridiculous.

Thanks
Yeah! That's true. But once you practice them you start to get them straight away, if that makes sense? So they're hoping you know them well enough to do so!
16. (Original post by krisshP)
What about liquid, gas? Say if you had H2O(l), would you split that into 2H+(l) and O^2-(l) or just leave it?
That's a smart question, and nope, liquids and gases don't split up. It's only aqueous reactants and products

Glad I could be of some help
17. (Original post by krisshP)
What about liquid, gas? Say if you had H2O(l), would you split that into 2H+(l) and O^2-(l) or just leave it?
You might want to watch this: http://www.youtube.com/watch?v=dXqelH1MxGw

she explains it really well!
18. (Original post by nukethemaly)
You might want to watch this: http://www.youtube.com/watch?v=dXqelH1MxGw

she explains it really well!
WOW you're right she explains it perfectly. My lazy teacher didn't teach Jack on this topic, he skipped it .

Thanks
19. (Original post by krisshP)
WOW you're right she explains it perfectly. My lazy teacher didn't teach Jack on this topic, he skipped it .

Thanks
Yeah, if I literally have any trouble with AS chemistry, the first thing I do is check her youtube page to see if she's covered it, if not then I check for Khan Academy. If not then I'll resort to asking my teacher or someone on student room.

Thankfully our chemistry department is quite helpful. But last year I had the ****test teachers ever. so I feel you!
20. (Original post by nukethemaly)
You might want to watch this: http://www.youtube.com/watch?v=dXqelH1MxGw

she explains it really well!
Ahh awesome, thanks for the link

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