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Edexcel - Chemistry Unit 2 - 4 June 2013

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Reply 660
Avatar for Gnome :)
Gnome :)
2
Original post by James A
You do get a data booklet, for all chemistry exams.


Not for AS :/
Original post by Gnome :)
Not for AS :/


That's odd, I got a data booklet for my AS Chem exams, this was back in June 2011 so I dunno if it's changed since.
Reply 662
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Goods
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Original post by charlieejobson
what section of the syallabus does this come under:

what colour is the vapour which forms when conc h2so4 is added to solid potassium iodide?


purple vapour, black solid bad, smell of eggs.
guys why is the angles in cyclohexanol 109.5?
Original post by charlieejobson
guys why is the angles in cyclohexanol 109.5?


Tetrahedral = Four bonding pair of electrons = 109.5
Original post by James A
Tetrahedral = Four bonding pair of electrons = 109.5


i dont see how its four :/
Original post by James A
Tetrahedral = Four bonding pair of electrons = 109.5


How is it tetrahedral if it's cyclo? :/


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Original post by charlieejobson
i dont see how its four :/


Cyclohexanol.

http://www.chemeddl.org/resources/models360/files/7966/cyclohexanol-lewis2.png

I'm assuming you are referring to the HCH bonds.
Original post by all_dolled_up
How is it tetrahedral if it's cyclo? :/


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no i understand now, its because there is 2 hydrogens directly attached to each carbon
Original post by charlieejobson
no i understand now, its because there is 2 hydrogens directly attached to each carbon


Ohh ok, yeah that makes sense now, I'd ignored the hydrogens and just tried to find the c-c bond :biggrin:

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Reply 670
Avatar for Jayqwe
Jayqwe
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Do we need to memorise the iodate titration equations?
Original post by Jayqwe
Do we need to memorise the iodate titration equations?


I think you only need to remember the thiosulfate ones, but it would be wise for you to know them.
Only remember the thiosulfate one. They will give you the other equation, e.g. one involving Potassium Iodide.
Reply 673
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Gunner121
Can anyone please explain why the bond angle in hydrogen bonding is 180 degrees.
Reply 674
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posthumus
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20
Original post by geor
If you were titrating acid (in burette) against alkali with the indicator as phenolphthalein; would the colour change be pink to colourless?

I'm so confused because when I used to do these titrations at my school the end point would always be pale pink, but the mark scheme doesn't seem to accept it..?


Well according to good old George here, Phenolphthalein is colourless in acid conditions

so it would go from Colourless to pink, then with excess alkali it will go purple :smile:
Original post by geor
If you were titrating acid (in burette) against alkali with the indicator as phenolphthalein; would the colour change be pink to colourless?

I'm so confused because when I used to do these titrations at my school the end point would always be pale pink, but the mark scheme doesn't seem to accept it..?


Maybe because you guys add the base from the burette and the acid is in the conical flask?

I am 100% sure the end point is colourless.
Original post by geor
If you were titrating acid (in burette) against alkali with the indicator as phenolphthalein; would the colour change be pink to colourless?

I'm so confused because when I used to do these titrations at my school the end point would always be pale pink, but the mark scheme doesn't seem to accept it..?


Remember that in all titrations, you always end up over shooting the end point, so the solution is either more acidic or alkaline, as opposed to being completely neutral.
Reply 677
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posthumus
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Original post by James A
Maybe because you guys add the base from the burette and the acid is in the conical flask?

I am 100% sure the end point is colourless.


George claims it's "pale pink"

Might be a mistake, I remember last our year had a dispute over it while we were going into the exam hall :tongue: I think the CGP says different
Original post by posthumus
George claims it's "pale pink"

Might be a mistake, I remember last our year had a dispute over it while we were going into the exam hall :tongue: I think the CGP says different


Wiki says that the neutral point is colourless, unless george facer is assuming the titration always overshoots. Honestly don't know.

I'm just sticking to the end point as pale pink.
anyone know any good definition websites

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