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

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??

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???

ok for the economic issue i wrote paragraph 9...wbu?

Oops got that wrong...anyway thanks!!

I don't think taking 100 and 0 is a good idea tbh.When you take one reading off that thermometer with ±0.5'C uncertainty,you do this to find the %uncertainty, (0.5/x) times 100% cuz you took only 1 reading.However if you take two readings like 25'c and 30'c you have a combined uncertainty of 2x( ±0.5) = 1.There you took the difference between the two values and you have to consider both the uncertainties i think.As for taking 100 and 0,if you divide ±0.5 by 0 you are gonna get ∞ or possibly a math error which is ignored and taken as zero.Not 100% sure though

can any1 pls tell me what to read on chemistry unit 1?

Ummm, I'm confused isn't alcohol considered as an organic solvent??? :s
Because Iodine gives a brown color in water, but it dissolves better in organic solvents giving a purple solution.


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If I put the right number for the value of the enthalpy change but forgot the sign, how much does it cost me? Do I get any marks at all for the question?

One mark for sign. You'll get the rest.

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Ahh Biology and Chemistry Unit 3b exams are a horrible way to start the exams off in my opinion, so many stupid mistakes from the start ;________;

I think they make us start with the unit 3 papers because they're supposed to be easy. (well, apparently not this time!) I'm trying my best to forget about that awful graph that came in the physics paper. I hope the grade boundaries go super low, but I think it's unlikely.

Good thing I decided not to take physics this year then haha

what are the observations seen in that iodobutane one ? is it only purple vapour

Relaxedexams man for the obswrvation one...what u c....i wrote like decrese in size, bubbles seen ...like tht...is it acceptable? and for the mass of mixture..was it 50 or 55? and the one after step 7 is re-distillation?

Are you talking about the carbonate observation? If so then I wrote solid disappears. What you wrote is also correct, not wrong.

Mass was mass of solution. That was 50?

Step 7 is fractional distillation.

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Are you talking about the carbonate observation? If so then I wrote solid disappears. What you wrote is also correct, not wrong.

Mass was mass of solution. That was 50?

Step 7 is fractional distillation.

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