Edexcel Chemistry Unit 5 June 19 2012

why are compounds miscible with water in steam distillation ???????????????!!!

because they can hydrogen bond with the water?

As i said above, the product has to be imiscible with the water for steam distillation to work. Your not required to know why this is the case.

Reply 781

iesians

6

Original post by James A

Prep of Cr2+ complex:

In a flask: Add pottasium dichromate, with concentrated HCl and zinc.

Use a delivery tube to connect to the other end containing a solution of sodium ethanoate.

Loosen the seal at top to let the hydrogen escape.

You will notice a colour change of orange to green and then to blue.

The orange is from the dichromate ions, the green is from the Cr3+ ions and the blue is from the Cr2+ ions.

Seal the cap of the screw. This will create pressure and hence this hydrogen will force the solution to the test tube containing the sodium ethanoate.

thankssss ...xx
but isnt HCl added from the tap funnel, it isnt already present in the flask.

Reply 782

areyousure?

13

Original post by This Honest

I don't think we have to know the synthesis of that...they will probably guide us or make us write down reagents during the synthesis

Fair enough then :smile:

I just read it on the spec and had a mini heart attack lol

Thanks :smile:

and best of luck dude!

Reply 783

iesians

6

Original post by James A

because they can hydrogen bond with the water?

As i said above, the product has to be imiscible with the water for steam distillation to work. Your not required to know why this is the case.

if they are immiscible then the bol part wouldnt be valid, but it is !! right ?

Reply 784

.snowflake.

14

Original post by iesians

why is phenol acidic ??! (2 marks)

electrons on the oxygen atom in the OH group get incorporated into the ring. Therefore, hydrogen becomes more delta + and so dissociate easier?

Reply 785

F1's Finest

21

Original post by iesians

if they are immiscible then the bol part wouldnt be valid, but it is !! right ?

Don't you have a textbook or something?

http://en.wikipedia.org/wiki/Steam_distillation

read the heading of the title 'Principle'

Reply 786

sailor27

Original post by giraffegiraffe

Yeah that's right - maybe to do with the fact that Zn isn't technically a transition metal?? Not really sure why, but that's definitely the right formula. Good luck today :smile:

In my book zinc is [Zn(H₂O)₃(OH)₃] which one is right??

Reply 787

sailor27

Original post by James A

Is it me or is zinc an exception when it comes to the number of ligands it can hold?

Why is it in the book that a normal precipitate is:

[Zn(H20)2(OH)2]

?

In my book zinc is [Zn(H₂O)₃(OH)₃] which one is right??

Reply 788

iesians

6

Original post by .snowflake.

electrons on the oxygen atom in the OH group get incorporated into the ring. Therefore, hydrogen becomes more delta + and so dissociate easier?

ummm no.
the phenoxide ion formed from the ionisation of phenol has electron lone pair on oxygen atom, this gets incorporated into the delocalised system of electrons in the ring. so the phenoxide ion cannot readily accept a proton, so this compound is stable and equilibrium is shifted to RHS forming more H+ ions.

Reply 789

verdikt

Original post by James A

Is it me or is zinc an exception when it comes to the number of ligands it can hold?

Why is it in the book that a normal precipitate is:

[Zn(H20)2(OH)2]

?

Nope, the book is wrong. Jun 2010, 21)b)ii)
It says it is H20 4 OH 2.

Only copper and zinc are affected when it comes to ammonia though.

Reply 790

iesians

6

Original post by James A

Don't you have a textbook or something?

http://en.wikipedia.org/wiki/Steam_distillation

read the heading of the title 'Principle'

wow ! if you dont wanna help then its okay , dont get angry.

Reply 791

This Honest

3

Original post by areyousure?

Fair enough then :smile:

I just read it on the spec and had a mini heart attack lol

Thanks :smile:

and best of luck dude!

Good luck to you too!

Reply 792

Chaofan88

10

okay so I have a few questions:

1)How do you calculate the final mass of product in a multi-step reaction where they give you the yield of each step?

2) How do you work out what the uncertainty of a piece of equipment is when they don't give you the 'manufacturer' uncertainty (but instead measurements taken from that piece of equipment eg. titres)?

3) any help surrounding purification/separation methods would be great as I'm never sure what would be good to use for what

Answer these questions three and you have mine and my cat's eternal love

Reply 793

F1's Finest

21

Original post by iesians

ummm no.
the phenoxide ion formed from the ionisation of phenol has electron lone pair on oxygen atom, this gets incorporated into the delocalised system of electrons in the ring. so the phenoxide ion cannot readily accept a proton, so this compound is stable and equilibrium is shifted to RHS forming more H+ ions.

??????????????????

Reply 794

This Honest

3

I just read the examiner report of jan 11 that someone drew the whole sturcture of edta4- :eek:

Reply 795

arnab

11

Original post by James A

Prep of Cr2+ complex:

In a flask: Add pottasium dichromate, with concentrated HCl and zinc.

Use a delivery tube to connect to the other end containing a solution of sodium ethanoate.

Loosen the seal at top to let the hydrogen escape.

You will notice a colour change of orange to green and then to blue.

The orange is from the dichromate ions, the green is from the Cr3+ ions and the blue is from the Cr2+ ions.

Seal the cap of the screw. This will create pressure and hence this hydrogen will force the solution to the test tube containing the sodium ethanoate.

do we need to know it??? :eek:

Reply 796

F1's Finest

21

Original post by iesians

wow ! if you dont wanna help then its okay , dont get angry.

I'm stating the facts by saying that the product and water has to be imiscible.

Is this so hard to understand.

I'm not getting angry but your complicating what i said.

Reply 797

iesians

6

Original post by James A

??????????????????

what ? the phenoxide ion is stable as it cannot accept a proton so its a weaker base and thus its conjugate acid (phenol) has to be strong.

Reply 798

iesians

6

Original post by James A

I'm stating the facts by saying that the product and water has to be imiscible.

Is this so hard to understand.

I'm not getting angry but your complicating what i said.

well, okay they are immiscible ( thats not hard)
but y ??!
i mean, shouldnt the product FORM H bonds with water to ACTUALLY seperate ?
then it has to be miscible ??! thats whats confusing.

Reply 799

xxbiologyxx

Original post by James A

concentrated

ahhh thanks! :smile:

Edexcel Chemistry Unit 5 June 19 2012

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