Chemistry Unit 2 Edexcel, Exam- 23rd May 2012

Reply 780

Arusa01

Original post by senz72

Good luck anyway! I'm off to do another 4 hour mass revision (with probably very little effect.)

Lol, good luck! :smile:

Reply 781

Godsavemefromexams

1

June 2009

20) ii) Suggest why 1-chlorobutane reacts with water via a different mechanism?

I dont understand the stable cation and steric hinderence!

HELPP SOMEONE

Reply 782

AS01

12

what happens when secondary alcohol is warmed with I₂ and NaOH?

Reply 783

AS01

12

Original post by Kasarna

Jan 2010 Question 10;

H2SO4(aq) + Ba(OH)2(aq) --> BaSO4(s) + 2HO2(l)

During the titration, the barium hydroxide was added until it was present in excess. The electrical conductivity of the titration mixture

A.) Increased steadily
B.) Decreased steadily
C.) Increased and then decreased
D.) Decreased and then increased

A bit confused on this question can someone please explain to me why the answer is D?

Would have thought the answer is B as the Barium Suplhate is a solid rather than aqueous ions and so cant conduct electricity.

this would be the type of question where I will guess :biggrin:

Reply 784

delphinas

Why CH3Br is immiscible with H20, but soluble in ethanol (C2H5OH) ?

Reply 785

qwerasd1

Original post by Kasarna

Jan 2010 Question 10;

H2SO4(aq) + Ba(OH)2(aq) --> BaSO4(s) + 2HO2(l)

During the titration, the barium hydroxide was added until it was present in excess. The electrical conductivity of the titration mixture

A.) Increased steadily
B.) Decreased steadily
C.) Increased and then decreased
D.) Decreased and then increased

A bit confused on this question can someone please explain to me why the answer is D?

Would have thought the answer is B as the Barium Suplhate is a solid rather than aqueous ions and so cant conduct electricity.

i thought it was D because the OH- ions would react with the H2SO4 till all the H2SO4 has reacted and since its in excess the amount of OH- ions will keep increasing which would increase the electrical conductivity. i think its that but im not sure

Reply 786

AS01

12

Original post by Godsavemefromexams

June 2009

20) ii) Suggest why 1-chlorobutane reacts with water via a different mechanism?

I dont understand the stable cation and steric hinderence!

HELPP SOMEONE

In this when water attacks the halogenoalkane then it first have to remove the Cl in the halogenoalkane right? so this form primary carbocation which is much less stable than tertiary carbocation formed in reaction 1.

Reply 787

Kasarna

1

Original post by AS01

this would be the type of question where I will guess :biggrin:

LOL and potentially lose 1 mark? As Tesco says Every Little Helps!

Original post by Godsavemefromexams

June 2009

20) ii) Suggest why 1-chlorobutane reacts with water via a different mechanism?

I dont understand the stable cation and steric hinderence!

HELPP SOMEONE

1-chlorobutane is a primary haloakane. A primary haloalkane cannot form a carbon cation as it will not be stable enough due to having a sufficient number of alkyl groups (only has one), around the carbon cation which donate electrons to it to stabilise it. Answers a bit long though am sure from that you will understand it, and definately gain the marks.

Reply 788

Blob2491

12

Ridiculously ill-prepared for this =[

Reply 789

itsmehello

2

June 2009, 49/80 to get an A

:eek:

Reply 790

im so fresh

12

rap is pac.
but anyway :smile:

can anyone link me the jan 2012 paper for this? will +rep

Reply 791

delphinas

Original post by itsmehello

June 2009, 49/80 to get an A

:eek:

Epic FAIL

Reply 792

Reversal

Original post by itsmehello

I need helP :frown:

The oxidation number of oxygen is always -2 apart from in H2O2

So in H202 is it -1??

Yes.
It's also +2 in OF2
and +1 in O2F2

Reply 793

Dovah13

Original post by delphinas

Why CH3Br is immiscible with H20, but soluble in ethanol (C2H5OH) ?

there is no non-polar part in h2O, only polar but ethanol has a polar and non-polar part so it can disolve bromemethane more than h20

Reply 794

Godsavemefromexams

1

Original post by itsmehello

June 2009, 49/80 to get an A

:eek:

OMG really!
This paper was **** hard though!

Reply 795

egg123

can someone tell me all the nitrogen oxides that absorb infared?

Reply 796

delphinas

Original post by Dovah13

there is no non-polar part in h2O, only polar but ethanol has a polar and non-polar part so it can disolve bromemethane more than h20

Thank you, nicely explained!

Reply 797

Dovah13

Original post by im so fresh

rap is pac.
but anyway :smile:

can anyone link me the jan 2012 paper for this? will +rep

http://www.thestudentroom.co.uk/showthread.php?t=1971547

Reply 798

AS01

12

Original post by delphinas

Why CH3Br is immiscible with H20, but soluble in ethanol (C2H5OH) ?

coz in H2O there are two H-bonds which require much more energy to break it bt in ethanol its just one H-bond so does not need much energy to break it. thats why CH3Br is miscible with ethanol.