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Chemistry Unit 2 Edexcel, Exam- 23rd May 2012

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Yaay thanks :biggrin:

Instead of transition state... the first step of Tertiary & Secondary Alcohol substitution is the 'rate determining step' instead ?? :smile:

Yesssss not problem

But not 100% about the RDS - i thought that is A2

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Reply 961

VRS

Original post by YellowAndBlack

Sn2 also requires a carbocation

Sn1
And is also techniqually a swap
You break off the C-Halogen bond for example - Let's say bromine = Forming a carbocation
A :Nu (nucleophile) attacks and attachs onto this carbocation - bromine is a product

And for Sn1 why are they less stable?

Because its something along the lines of

The charge on the carbon is high

Whereas on tertiary - the methyl groups have a positive effect on the central carbon making it less prone

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Reply 962

Blob2491

Original post by EffKayy

Good luck =)
Thanks for coming on scriblink (!)
k.

no problem =D
Good luck!

Reply 963

2006019

When do you use methyl orange and when phenalphthalein?
and methyl orange end point is red -> orange and phenalphthalein is colourless to pink/purple?
Really hope this is a nice paper..

Reply 964

VRS

Original post by 2006019

When do you use methyl orange and when phenalphthalein?
and methyl orange end point is red -> orange and phenalphthalein is colourless to pink/purple?
Really hope this is a nice paper..

In alkali

Methyl orange goes from yellow to orange

In acid

It is red to orange

phenolphthalein is pale pink in acid and colourless in acid - to pale pink

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(edited 11 years ago)

Reply 965

K. Kush

Does anyone have the unofficial mark scheme for the edexcel chemistry unit 1 paper sat last week?

Reply 966

2006019

Original post by VRS

Thank you!

Reply 967

Megaman1995

oh my god this is soo hardd

Reply 968

VRS

Original post by AmrinderRai

Yaay thanks :biggrin:

Instead of transition state... the first step of Tertiary & Secondary Alcohol substitution is the 'rate determining step' instead ?? :smile:

Just read that sn1 is RDS - two step blah blah blah....

Second attack is fastest so first step is RDH

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Reply 969

existinggirl

is this exam definitely an afternoon exam?

Reply 970

itsmehello

Original post by oli_G

Because at first the barium removes ions from the solution, as it forms barium sulfate - this decreases the electrical conductivity as there are fewer charge carriers.

As more and more barium hydroxide is added more this effect is counteracted by the increase in the number of ions so the electrical conductivity then increases.

Hence, D :smile:

Oh okay thanks!!

Reply 971

itsmehello

Do we need to know major product and minor product??

Reply 972

salvequamtu

Original post by itsmehello

Do we need to know major product and minor product??

Its highly unlikely to come up but all you need to know is that the Hydrogen will go to the carbon that already has the most hydrogens (usually the end carbon).

Reply 973

MissRiah12345

Original post by itsmehello

Do we need to know major product and minor product??

I think so. In one paper we had to recall minor and major from the addition of bromine to propene and we had to show the mechanism for the major product and draw the structural minor product :smile:

(edited 11 years ago)

Reply 974

senz72

I'm literally screwed for this exam!