The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

Need help with this question please!

ooo.PNG65.9KB
Reply 1
Avatar for Pigster
Pigster
20
What have you got for the previous parts to the Q and why are you stuck on the last part?
Reply 2
Avatar for Adorable98
Adorable98
OP
15
Original post by Pigster
What have you got for the previous parts to the Q and why are you stuck on the last part?




Well for the last question cos we're looking for the number of moles, I decided to use this formula Number of moles = Number of particle/6.0 x 1023 so 2 / 6.0x1023 but my answers wrong?!:s-smilie:
ooo.PNG67.9KB
Reply 3
Avatar for Pigster
Pigster
20
You started with 0.001 mol of I2

0.00063 mol of I2 remained after the SO2 had reacted.

How many mol of I2 must have reacted with SO2?

Applying the second reaction they gave you (the one in part b), how many mol of SO2 were there in the 100 m3?
Hi Adorable98

Attached is a work through of the answers. I hope this helps (pretty much what Pigster was eluding to, so thought I would finish it off as a worked example). If you need any revision notes or questions/model answers etc. check out my 100% free website www.scienceskool.co.uk

Have fun

Alex

Answer Photo.jpg
Reply 5
Avatar for Adorable98
Adorable98
OP
15
Original post by Pigster
You started with 0.001 mol of I2

0.00063 mol of I2 remained after the SO2 had reacted.

How many mol of I2 must have reacted with SO2?

Applying the second reaction they gave you (the one in part b), how many mol of SO2 were there in the 100 m3?

I see, thank you!:smile:
Original post by ajsullivan
Hi Adorable98

Attached is a work through of the answers. I hope this helps (pretty much what Pigster was eluding to, so thought I would finish it off as a worked example). If you need any revision notes or questions/model answers etc. check out my 100% free website www.scienceskool.co.uk

Have fun

Alex

Answer Photo.jpg


Woow, Thaanks a loot!! :h: I'd definitely check it out!!:smile:
Reply 6
Avatar for Chem98
Chem98
2
Original post by Pigster
You started with 0.001 mol of I2

0.00063 mol of I2 remained after the SO2 had reacted.

How many mol of I2 must have reacted with SO2?

Applying the second reaction they gave you (the one in part b), how many mol of SO2 were there in the 100 m3?


Original post by ajsullivan
Hi Adorable98

Attached is a work through of the answers. I hope this helps (pretty much what Pigster was eluding to, so thought I would finish it off as a worked example). If you need any revision notes or questions/model answers etc. check out my 100% free website www.scienceskool.co.uk

Have fun

Alex

Answer Photo.jpg


Hello there,
Sorry to bother you but I don't understand why you subtracted the remaining moles of I2 from the starting moles of I2 ?
The remaining I2 reacted with thiosulfate not with SO2!
ONLY 0.001 moles reacted with SO2 and the remaining I2 reacted with thiosulfate.
So shouldn't the number of moles be 0.001 moles?:smile:

Chem98
Reply 7
Avatar for Pigster
Pigster
20
Let's pretend that you started with 10 mol of I2.

You react those 10 mol with an unknown amount of SO2.

The remaining I2 reacted with S2O32-.

You find, by calculation, that there must have been 4 mol of I2 that reacted with your S2O32-.

Where did the rest of the I2 go? It reacted with the SO2! How much I2 reacted with the SO2? 10-4=6 mol
What Pigster said, your finding the difference.

Alex
Original post by ajsullivan
Hi Adorable98

Attached is a work through of the answers. I hope this helps (pretty much what Pigster was eluding to, so thought I would finish it off as a worked example). If you need any revision notes or questions/model answers etc. check out my 100% free website www.scienceskool.co.uk

Have fun

Alex

Answer Photo.jpg


Hi ajsullivan,

Sorry to bother you, but why can starch be used as an indicator for this titration (part a)?

Thanks,

Jasmine
The titration involves the conversion of I2 into I-.

I2 forms a blue-black solution in the presence of starch whereas I- is colourless.
Original post by Pigster
The titration involves the conversion of I2 into I-.

I2 forms a blue-black solution in the presence of starch whereas I- is colourless.


Thank you Pigster! I understand now!

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you