Chemistry Unit 6B [6CH08][Edexcel][International Candidates][22.05.2012]

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Hey Guys!! Now how do i prepare for the upcoming UNITS???
Plus I think the chromatography can be improved by using more silica plates in a column chromatographic manner. This would cause more interaction with the stationary phase. (Just guessing)...

Reply 241

k121op

i just remembered that i accidentally wrote [Cr(NH4)6]3+ instead of [Cr(NH3)6]3+....totally ****ed up!!!

Reply 242

laugh123

The % copper in was about 46.1 % it wouldnt make sense if it were 92.2%

Reply 243

gogo1994

how did you calculated the mass of cu in q3?

Reply 244

poopypie

Original post by sajidmatin

It was a pretty good paper.

For HCl test, you can write bleaching of blue damp litmus paper, or white smoke with NH3 gas. It was two marks though, so it wrote both.

Yeah i wrote the same thing for this one. We'll only get one mark- if we're lucky. The question asked for a test for halides and then what you would observe for HCl. We were supposed to write the one with silver nitrate. I was so pissed when I realized. 1-2 marks gone !!!! :mad:

Reply 245

iesians

Original post by laugh123

The % copper in was about 46.1 % it wouldnt make sense if it were 92.2%

wrong! it completely makes sense if it was 92.2% ! lol ! u probably took the mass on 25cm3, we had to convert that to 250cm3 .....

Reply 246

sasha_olemui

Original post by iesians

wrong! it completely makes sense if it was 92.2% ! lol ! u probably took the mass on 25cm3, we had to convert that to 250cm3 .....

exactly

Reply 247

sasha_olemui

Original post by gogo1994

how did you calculated the mass of cu in q3?

i still rmb the no. of moles of Cu2+ in the sample being titrate is 3.05x10^-3
continue doing.... no of moles of Cu2+ in the coin: 3.05x10^-3 x 250/25 = 0.0305
mass of Cu2+ in the coin: 0.0305 x 63.5 = 1.93675 g
percentage : 1.93675/2.10 x 100% = 92.2%

Reply 248

iesians

ok everyone the moles of thiosulphate and Copper were same right ..?! why the heckkkkk was the question for 2 marks then ..?!??! did v have to show all the calculation like first halving it and then doubling it ! we would get the same f*****g answer ! i just wrtoe same as thiosulphates and wrote the value !!!! will i get 2 marks ??!?!?!?!!? i wanna bawl my eyes out nowwww !!!!!!!!! :frown:

(((((((

Reply 249

bsblitter

Original post by sasha_olemui

Can u remember whether the number of moles in a coin was in a separate questions or not? Did it ask for the number of mole in the sample then the number of moles in the coin?

I know it sounds like a weird question to ask but just trying to remember whether i multiplied by 10 or not.

Reply 250

iesians

Original post by bsblitter

it asked to find number of moles in coin in a second part ! and yes even i multiplied by 10 ! that is correct !

Reply 251

sasha_olemui

Original post by bsblitter

nah it didn't ask for the number of moles in the coin, it asked directly for the mass of Cu in the coin in part c, then part d the percentage.
(or perhaps directly asking the percentage?? i can't quite rmb. but one thing i'm sure is that it didn't ask for the no. of moles in the coin :P )

Reply 252

kitriviolet

greattttt i got that as well! :smile:

Original post by iesians

wrong! it completely makes sense if it was 92.2% ! lol ! u probably took the mass on 25cm3, we had to convert that to 250cm3 .....

Reply 253

sasha_olemui

Original post by iesians

it asked to find number of moles in coin in a second part ! and yes even i multiplied by 10 ! that is correct !

wasn't part b asking for the number of moles in the sample being titrate??

Reply 254

iesians

Original post by sasha_olemui

wasn't part b asking for the number of moles in the sample being titrate??

ummmmm im not sure ...i think it was part c which asked about the ORIGINAL SAMPLE ! so then part b shouldve been the one with the same answer as part A.....

Reply 255

iesians

guys if part b was same as part a , why was part b of 2 marks ..?!?!?!!!?!!?!? edexcel pisses me off !!

Reply 256

sasha_olemui

Original post by iesians

guys if part b was same as part a , why was part b of 2 marks ..?!?!?!!!?!!?!? edexcel pisses me off !!

yea part b same answer as part a.......i am confused too!!
seeing it worths 2 marks, i wrote one step.....divided it by two then multiply it by 2 ._. meaningless LOL

Reply 257

iesians

Original post by sasha_olemui

yea part b same answer as part a.......i am confused too!!
seeing it worths 2 marks, i wrote one step.....divided it by two then multiply it by 2 ._. meaningless LOL

lol ikr ! i wish i could have done tht ! i did all the calculation on calculator and when the answer was coming same i just wrote the same value ! without seeing its of 2 marks ! edexcel is so effin dumb !! will i get the marks ? whatdya think ?

Reply 258

MujtabaM

Original post by iesians

Yeah that was weird I spent 5 extra mins just to make sure there wasn't some hidden trick that I missed out...

I think one mark for the answer and one mark for saying mol ratio is 1:1 :rolleyes: