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# Edexcel IAL Chemistry Unit 3 WCH03 May June 2016 Discussion

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1. (Original post by RiccardoRocco)
Percentage error was 41%
Enthalpy was -430 as
Energy transferred was 21564--- (0.32*300 +4.2*400)* 12 == 21564
Moles = 0.05
No idea how you guys are getting -418
That's cuz we didn't round of to 2dp as i read in the examiner report that if there are any furthur calc then don't round and use the exact value given in the calculator
2. (Original post by Ahmed3651998)
same here givin' physics also!
I hope physics is easier
3. (Original post by Sumaiyya1999)
That's cuz we didn't round of to 2dp as i read in the examiner report that if there are any furthur calc then don't round and use the exact value given in the calculator
So are we right?
4. (Original post by RiccardoRocco)
So are we right?
I think cz 80% of my classmates got -418 as the answer
5. (Original post by Sumaiyya1999)
I think cz 80% of my classmates got -418 as the answer
Even using 2sgf, your value would then be GREATER, how did they get -418?
6. (Original post by RiccardoRocco)
Even using 2sgf, your value would then be GREATER, how did they get -418?
We used 3sf and it gave the value 418
7. (Original post by RiccardoRocco)
Percentage error was 41%
Enthalpy was -430 as
Energy transferred was 21564--- (0.32*300 +4.2*400)* 12 == 21564
Moles = 0.05
No idea how you guys are getting -418
You only used 0.05 moles,We used 0.0516 which is more accurate.
8. (Original post by RiccardoRocco)
Even using 2sgf, your value would then be GREATER, how did they get -418?
Do the math.
9. What about thermometer and collection flask, Im pretty sure that thermometer is a must
What about thermometer and collection flask, Im pretty sure that thermometer is a must
I think there will be options
11. what about the last question?
12. Hello people do you think in the major product questiom they'd accept ioohexanol. Because when I read the word in situ I assumed with sulphuric acid and so iodide with be oxidissed to iodine and so I wrote about the mechanism of alkene and iodine. As OH- is also present and it's a better nuclephile hence iodoalkane. I think it's wrong but any change of being accepted?
13. How much will i score if i wrote the reaction as follows 2KHCO3(s)___K2O(s)+H20(g)+2C02(g )
(He said water vapour so it is in the gas state)
And considering the test for iodine atom i said nitric acid and silver nitrate solution ,giving a yellow precipitate,i believe it is correct because water dissolves the halogenoalkane of course not as efficient as the ethanol but at least the ppt will appear and reaction will occur ... Need your opinions guys !!!
14. (Original post by sharin22)
I believe the first suggestion can be both valid and not valid depends on how you elaborate .. The second is invalid and the last two are valid .. I am just assuming as i dont know the correct answer
15. (Original post by Raghdaelgedawy)
How much will i score if i wrote the reaction as follows 2KHCO3(s)___K2O(s)+H20(g)+2C02(g )
(He said water vapour so it is in the gas state)
And considering the test for iodine atom i said nitric acid and silver nitrate solution ,giving a yellow precipitate,i believe it is correct because water dissolves the halogenoalkane of course not as efficient as the ethanol but at least the ppt will appear and reaction will occur ... Need your opinions guys !!!
1 mark for balancing and state symbols I guess. And why the nitric acid when you haven't even added sodium hydroxide? The purpose is to neutralize OH- which isn't really present.
16. (Original post by Ayesssshaaa)
1 mark for balancing and state symbols I guess. And why the nitric acid when you haven't even added sodium hydroxide? The purpose is to neutralize OH- which isn't really present.
. Silver nitrate is already aqueous and so it has water that donates OH- , the sodium hyroxide is actually used beacuse it provides Stronger OH- than water so it kind of accelerates the reaction
17. (Original post by Raghdaelgedawy)
. Silver nitrate is already aqueous and so it has water that donates OH- , the sodium hyroxide is actually used beacuse it provides Stronger OH- than water so it kind of accelerates the reaction
I get that part. But you've mentioned nitric acid without mentioning sodium hydroxide so what's the use? the OH- is coming from water and replacing I and the I- reacts with Ag+ to form ppt. What's the acids role in this until and unless you've added sodium hydroxide which you'd neutralize with the acid.
18. (Original post by Ayesssshaaa)
I get that part. But you've mentioned nitric acid without mentioning sodium hydroxide so what's the use? the OH- is coming from water and replacing I and the I- reacts with Ag+ to form ppt. What's the acids role in this until and unless you've added sodium hydroxide which you'd neutralize with the acid.
May the examiner be kind and omit the nitric acid ... Will i lose the two marks i already have mistakes !!!!
19. (Original post by Raghdaelgedawy)
May the examiner be kind and omit the nitric acid ... Will i lose the two marks i already have mistakes !!!!
Nope I think you'll get the second mark and don't worry everyone found the paper quite tough so a low threshold
20. (Original post by Raghdaelgedawy)
How much will i score if i wrote the reaction as follows 2KHCO3(s)___K2O(s)+H20(g)+2C02(g )
(He said water vapour so it is in the gas state)
And considering the test for iodine atom i said nitric acid and silver nitrate solution ,giving a yellow precipitate,i believe it is correct because water dissolves the halogenoalkane of course not as efficient as the ethanol but at least the ppt will appear and reaction will occur ... Need your opinions guys !!!
Omg lol I can't believe I wrote exactly the same thing as you for the iodine atom test! But the thing is I specifically wrote add nitric acid and silver nitrate solutions and I underlined it. Do you think I will get the mark? I think the second mark we will both get because the yellow precipitate has to form.

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Updated: June 8, 2016
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