Edexcel Chemistry A2 Unit 5 ~ Wednesday 19th June 2013 (Now Closed)

Whoever George Lewis is, thank you for those notes!! seriously they are spectacular.

Reply 1861

Original post by AtomicMan

When would you use steam distillation?

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to separate organic products which might otherwise decompose from sustained heating.

Reply 1862

Bord3r

Original post by blackraven

Whoever George Lewis is, thank you for those notes!! seriously they are spectacular.

Second this. Brilliant notes.

Reply 1863

Original post by AtomicMan

When would you use steam distillation?

Posted from TSR Mobile

To prevent a compound from decomposing when heated up.

In other words, we're able to distil a product at a lower temperature than it's boiling point. Extremely useful if we want to maximise the product yield.

Reply 1864

AtomicMan

Original post by Bord3r

Second this. Brilliant notes.

Link please?

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Reply 1865

Original post by posthumus

But the option said aq ammonia :frown:

or does that no have much significance ?

& Thank-you :smile:

Yeah aq ammonia is what the reactions take place with Ccording to the edexcel blue book.... No problem :wink:

Reply 1866

How do you know if a product shows optical activity? Is that if it contains a chiral carbon?

Reply 1867

Original post by Bubblezzzz

Good luck everyone! X
hope you all get a*s

Aren't you lovely ... I hope we all do too :smile:

Reply 1868

Original post by James A

How do you know if a product shows optical activity? Is that if it contains a chiral carbon?

No, you use a polarimeter to test whether it rotates the plane of polarisation of plane polarised light. If it does it is optically active :smile:

Edit; yes that is actually, but it's not a test for it

(edited 10 years ago)

Reply 1869

Original post by jojo1995

No, you use a polarimeter to test whether it rotates the plane of polarisation of plane polarised light. If it does it is optically active :smile:

Edit; yes that is actually, but it's not a test for it

So does that mean a racemic mixture is optically active? :smile:

Reply 1870

posthumus

Original post by James A

So does that mean a racemic mixture is optically active? :smile:

racemic solution contained same amount of both enantiomers which rotate plane polarised light in opposite directions equally...

since they're in equal amounts there will be no optical activity of the mixture as a whole

Reply 1871

randyaloul

Original post by James A

How do you know if a product shows optical activity? Is that if it contains a chiral carbon?

No, it might have a chiral carbon but it might be a racemic mixture, in that case it's not optically active. All optically active substances have chiral carbon atoms, but not all molecules with chiral carbon atoms are optically active. If that makes any sense :smile:

Reply 1872

Original post by James A

So does that mean a racemic mixture is optically active? :smile:

No a race mic mixture isn't as although each isomer would rotate the ppl, they would do so in opposite directions and so they cancel out. So race mic mixture had no overall effect on ppl

Reply 1873

alla soup

Does anyone have a link for jan 2013 mark scheme ?

Reply 1874

Gnome :)

Original post by James A

How do you know if a product shows optical activity? Is that if it contains a chiral carbon?

Stumbled across this wonderful video earlier: http://www.khanacademy.org/science/organic-chemistry/stereochemistry-topic/chirality-r-s-system/v/introduction-to-chirality. The example videos are pretty useful. A Chiral molecule will rotate the plane of plane polarised light.

(edited 10 years ago)

Reply 1875

Cheers everyone :yy:

I got it now xD

Reply 1876

6CH05 Jan 2013 mark scheme.pdf230.2KB

Original post by alla soup

Does anyone have a link for jan 2013 mark scheme ?

attached

Reply 1877