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# AS Chemistry- helping each other out! watch

1. (Original post by thymolphthalein)
Hey, I answered you on your thread earlier but I didn't quote so I don't know if you saw it. I'll just repeat my answer here too.

I think the equation is:

Concentration in ppm = (mass or volume of component/mass or volume of solution) X 1000000

I don't think there's much to ppm other than that?

You didn't give the volume of the original sample of air but I recognize that question, it's from the May 2012 Unit 2 paper which I did recently and it states that the sample of air was 100m3.

So. (4.743x10-6/100) x 106 = 0.04743 ppm
Thank you for answering my question! I switched to Biology soon after so I was meant to read, understand and reply when I came back to Chemistry (never happened). Again thanks >.<
2. "Write an equation for the reaction of iron with antimony sulfide to form antimony andiron(II) sulfide"
The question gives you Sb2S3 for antimony sulfide but how do you know what the formula is for iron(ll) sulfide???? :/
3. (Original post by Signorina)
"Write an equation for the reaction of iron with antimony sulfide to form antimony andiron(II) sulfide"
The question gives you Sb2S3 for antimony sulfide but how do you know what the formula is for iron(ll) sulfide???? :/
Well what group is S in? Group 6. They usually form 2- ions when reacted with metals. And it says iron (II) sulfide which means that the oxidation number for iron is +2. So it's 2 to -2 already and the "charge" balances so it's just FeS

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4. (Original post by Signorina)
"Write an equation for the reaction of iron with antimony sulfide to form antimony andiron(II) sulfide"
The question gives you Sb2S3 for antimony sulfide but how do you know what the formula is for iron(ll) sulfide???? :/
Use your knowledge of oxidation states - Iron(II)Sulfide: We're aware that Iron, in this instance, will have an oxidation state of +2, we're also aware of the fact that Sulfur will always have an oxidation state of -2 (Group 6), so in order to equate the oxidation state value to 0 we'll require one atom of Iron and one atom of Sulfur, thus creating Iron Sulfide: FeS!
5. (Original post by C0balt)
Well what group is S in? Group 6. They usually form 2- ions when reacted with metals. And it says iron (II) sulfide which means that the oxidation number for iron is +2. So it's 2 to -2 already and the "charge" balances so it's just FeS

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(Original post by Zer0.)
Use your knowledge of oxidation states - Iron(II)Sulfide: We're aware that Iron, in this instance, will have an oxidation state of +2, we're also aware of the fact that Sulfur will always have an oxidation state of -2 (Group 6), so in order to equate the oxidation state value to 0 we'll require one atom of Iron and one atom of Sulfur, thus creating Iron Sulfide: FeS!
Ahhhhhh I get it now thank you !!!!!!!

6. hey I'm a bit confused on this question- would be grateful for any help so I get that the green colour disappears when the NaOH is added because it reacts with either acid on the right and the equlibrium has to shift to the right to restore the acid. My question is why doesn't the NaOH react with the chlorine? In this case the equilibrium would shift the other way ....
sorry if this is confusing!
7. if anyone could help me with this I'd be really grateful - it's not like the other Hess' cycles
8. (Original post by VetVikki)
if anyone could help me with this I'd be really grateful - it's not like the other Hess' cycles
The way I teach this to my students is to get them to set up the Hess cycle and then say that

anti-clockwise arrows = clockwise arrows

So;

+ 963 + ΔH = -432 + (-75)

ΔH = -1470
9. for ocr f322

what do you need to know for these points on spec

- describe benefits of developing chemical processes with high atom economy in terms of fewer waste products

- explain a reaction may have a high % yield but a low atom economy

thanks

10. Wat
11. (Original post by hibaj)
for ocr f322

what do you need to know for these points on spec

- describe benefits of developing chemical processes with high atom economy in terms of fewer waste products

- explain a reaction may have a high % yield but a low atom economy

thanks

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For spec,recognise which bonds vibrate,like OH in water,C=O in co2 and CH in methane.
Learn how to interprete what functional groups are in a compound from the spectrum (IR)
Learn about the fragments (mass spec) which ones can come from a compound (use molar mass) and.that they are unique.
Learn about applications of both.

Chemical processes with high atom economy means less waste products are produced,so it is.more sustainable, more desired product, cheaper as less money spent disposing of waste products and separating them from the desired product.

High percentage yield means most of the reactants are converted into the products, but it can have. Alow atom economy as most of the products could be the waste product and not the desired product.
Hope this helps .
12. (Original post by Dinaa)

Wat
Wow, my over board studying of green chemistry might actually pay off. I'm going to attempt this.

*ahem*
Initiation:
CCL2F2 ----> CClF2• + Cl•

Propagation:
Cl• + O3 ----> ClO• + O2

ClO• + O3 ----> 2O2 + Cl•

Termination:
They'll probably accept any two free radicals combining.

ClO• + Cl• ----> Cl2O

It's a serious issue because the free radical regenerates and continues to break down ozone into oxygen depleting the amount of ozone we have. Edit: Due to the depletion, more UV rays enter and causes skin cancer and other bad things.
So overall we get something like:
2O3 --> 3O2

Note: still kind of iffy about the propagation steps so please do check them with a mark scheme or something.
13. Hello

On this paper for 3 a iv) why don't you add the moles, to make 0.2 and divide the enthalpy by 0.2. the mark scheme says 0.1 but this is strange since the two chemicals are mixing and reacting?
14. (Original post by TeachChemistry)
The way I teach this to my students is to get them to set up the Hess cycle and then say that

anti-clockwise arrows = clockwise arrows

So;

+ 963 + ΔH = -432 + (-75)

ΔH = -1470
Thankyou for replying What do you mean when you say "anti-clockwise arrows = clockwise arrows" and with the arrow along the bottom for the reaction equation, is that a + or - sign, that's where I'm confused
15. (Original post by thymolphthalein)
.
i like your name
16. (Original post by C0balt)
i like your name
I like yours too.

Phenolphthalein was taken.
17. (Original post by thymolphthalein)
I like yours too.

Phenolphthalein was taken.
Cobalt was taken lol
now I know how to spell phenolphthalein thanks to your name
18. Help with redox ewuation for SO4 2- ---> SO2
19. (Original post by Dinaa)
Help with redox ewuation for SO4 2- ---> SO2
S goes from 6 to 2 (it is reduced) - hope this helps
20. (Original post by VetVikki)
Thankyou for replying What do you mean when you say "anti-clockwise arrows = clockwise arrows" and with the arrow along the bottom for the reaction equation, is that a + or - sign, that's where I'm confused
See below.
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