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Edexcel 6CH07/01- May 8th 2013 - AS Chemistry Unit 3B

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How many marks was that? Damn I said black solid disappears. Totally forgot iodine forms a purple solution with non polar solvents :s-smilie:

Maybe they will mark both since all iodine will not dissolve?

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I think they'll mark...I had forgotten about that D:

Reply 161

wbrian

How many marks was the iodo butane question and how much do they give the final Mark out of ,is it 100

Reply 162

Munchee

Original post by sahashuvo

Hydrogen Iodide has enough reducing power to reduce Concentrated Sulfuric acid so yield would be lower.

Oops got that wrong...anyway thanks!!

Reply 163

rockstar101

Original post by Relaxedexams

Error x2
Therefore error is 1.

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My teacher told me to never multiply by 2 for the new exams cause i did that in my mock n got it wrong :s-smilie:

. Omg no. Serious like for sure?
thanx though :smile:

Reply 164

awesomesoccerfan

Original post by Relaxedexams

Yep. That is what I got. % error = 2.15? And you rounded it to 2.2?

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I got 2.19 something so i kept it to 2s.f. Will i still get the mark?What do u reckon?

Reply 165

Relaxedexams

Original post by awesomesoccerfan

I got 2.19 something so i kept it to 2s.f. Will i still get the mark?What do u reckon?

Im guessing you used 47 as temperature change? I used temperature change of solution. Either way they will most probably award marks.

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Reply 166

Relaxedexams

Original post by rockstar101

My teacher told me to never multiply by 2 for the new exams cause i did that in my mock n got it wrong :s-smilie:

. Omg no. Serious like for sure?
thanx though :smile:

You have to take two temperature readings, so there will be 2 errors of 0.5. Total error = 2 (0.5)=1

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Reply 167

awesomesoccerfan

Original post by Relaxedexams

Im guessing you used 47 as temperature change? I used temperature change of solution. Either way they will most probably award marks.

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I used 45.6(actual difference used during enthalpy change calculation). 1/45.6 x 100 and got 2.19.

Reply 168

Relaxedexams

Original post by awesomesoccerfan

I used 45.6(actual difference used during enthalpy change calculation). 1/45.6 x 100 and got 2.19.

That is what I did. Maybe I got 2.19 as well :tongue:

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Reply 169

KhawlaM

When drawing the distillation are we allowed to use a pencil??? :O

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Reply 170

Sweet Strawberry

Yes of course!

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Reply 171

MrNevermind

For the question 'why thiosulfate is used to wash the mixture instead of water', is it because iodobutane does not mix with water so it cannot be washed? If you reckon my answer is wrong, what's your answer?

Reply 172

RoyalBlue7

Original post by MrNevermind

The only places thiosulphate exists in our specs is in reaction of halogens and iodometric titrations (iodine with thiosulpate).
So to remove unreacted iodine by reduction to iodide ions which dissolves in the aqueous layer and can be removed by separation.
So answer is adding just water does not dissolve iodine but thiosulphate solution does.

Always reflect the specification, or is there another answer?

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Reply 173

rockstar101

Hey do any of you have the question paper like for bio it was posted up. Pls post this one as well. I just want to clarify some question. Thanx in advance :smile:

can i find it on scribd?

Reply 174

Tamerdakkak

What's the empirical formula in the first question ?

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Reply 175

Relaxedexams

Original post by Tamerdakkak

What's the empirical formula in the first question ?

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C3H8O or C3H7OH

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Reply 176

kiasha

Original post by KhawlaM

You are probably right. I forgot about the organic solvent, so I wrote instead that the brown color will disappear :s

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hey alcohol is polar right?? it can form hydrogen bonds with water..when iodine dissolves in polar solvents it gives a brown color. so shouldnt it be brown???

Reply 177

kiasha

Original post by Relaxedexams

You have to take two temperature readings, so there will be 2 errors of 0.5. Total error = 2 (0.5)=1

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if you take the temperature difference wont the error cancel out? i mean 100-0 is 100 and 101-1 is also a hundred. so even if error was present in the thermometer reading the temperature difference obtained would still be accurate right??

Reply 178

immastudent

What's the answer for the "why do we use dilute sodium thiosulphate solution instead of water?" question??

AND BTW..i failed in my physics unit3B exam... TT____TT
I made ONE mistake and it cost my whole ques...I'm crying sooo much nowwww..