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EDEXCEL UNIT 2 (RESIT) 2016 Answers

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Reply 40
Avatar for Hdb
Hdb
Pretty sure the iodine value was ~80.6g
Original post by ToxicPhantom007
The number of moles you got is right. Though they asked that thses moles are in 0.2 g of oil so in 100 g of oil we had to multiply moles by 500 and the moles came were 0.45 something
0.45 x 2(126.9)= 114.8 g
80 is wrong

Wasn't the moles 0.3 or something tho?
Original post by Hdb
Pretty sure the iodine value was ~80.6g


I reckon so
Reply 43
Avatar for scrlk
scrlk
7
Original post by RUNSran
Oh I get it .. do you think i will the marks that follows if i carry my error forward?


ECF would definitely apply so you've lost maybe 1/2 marks max on that calculation.
Reply 44
Avatar for Rsangha
Rsangha
I got 107
Reply 45
Avatar for Hdb
Hdb
Original post by Crespo0008
I reckon so

Everyone apart from 1 person I know got that value lol! It was more of a unit 4 calculation haha
What did everyone get for the very last question about the sample and iodine-would it increase, decrease or neither?
Reply 47
Avatar for scrlk
scrlk
7
Original post by mayaham12
What did everyone get for the very last question about the sample and iodine-would it increase, decrease or neither?


Increased titre, lower iodine value.
Reply 48
Avatar for corpeal
corpeal
9
How did people explain what was going in step 1 and 2 of the thermal decomposition of Mg(NO3)2
Reply 49
Avatar for scrlk
scrlk
7
Original post by corpeal
How did people explain what was going in step 1 and 2 of the thermal decomposition of Mg(NO3)2


Thought water would come out in step 1, then it would turn to steam in step 2 after enough heating.
Original post by RUNSran
yeah i got something similar - dont know how people got 80 something. What was the moles of s203 that reacted in the blank titration?


0.004 moles? i don't remember exactly
what did you get? ^_^
Original post by scrlk
Increased titre, lower iodine value.

same :biggrin:
Reply 52
Avatar for Hdb
Hdb
Does anybody know the value of the concentration calculation in the multiple choice?
i got 0.3725 or something like that i cant remember fully
Reply 54
Avatar for JoeyTr
JoeyTr
8
Original post by beanigger
i got 0.3725 or something like that i cant remember fully


0.001-0.000365=0.000635, 0.000635x500=0.3175
126.9x2x0.3175=80.58g
(edited 7 years ago)
Reply 55
Avatar for corpeal
corpeal
9
Original post by Hdb
Does anybody know the value of the concentration calculation in the multiple choice?



0.33
Reply 56
Avatar for Kaka121
Kaka121
2
Hey I have 3 questions about section A
What was the 1st answer? I put C (3)
What was the conc of na2s04? I guessed and put 0.5
What was organic molecule using wave number And? I out the aldehyde one
Ty guys
Original post by corpeal
How did people explain what was going in step 1 and 2 of the thermal decomposition of Mg(NO3)2


Step 1: I assumed that some of the Mg(OH)2 had precipitated out of the solution and that upon heating its solubility increases and so dissolves back into it.

Step 2: Water was evaporating and CaO was being formed via thermal decomposition
Reply 58
Avatar for JoeyTr
JoeyTr
8
Original post by Kaka121
Hey I have 3 questions about section A
What was the 1st answer? I put C (3)
What was the conc of na2s04? I guessed and put 0.5
What was organic molecule using wave number And? I out the aldehyde one
Ty guys


Yeah first one I put C too,
I put 0.33 for the concentration.
And I take it you mean the IR spectra, where I also put the aldehyde.
Reply 59
Avatar for Kaka121
Kaka121
2
Original post by JoeyTr
Yeah first one I put C too,
I put 0.33 for the concentration.
And I take it you mean the IR spectra, where I also put the aldehyde.

Ohh ok are you sure C was right?! And how did you get 0.33?
Lastly did you also get 0.4 for uncertainty? I think I got 19/20 in section A hopefully

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