Edexcel Unit 1 June 2011 Discussion.

hi guys for the crystal question i describe how it is formed will they at leat give me some marks i said filter leave crystals to dry , leave them to cool? will i get at least 1 mark or 2?? for the three eeasons I PUT LOSS OF HEAT TO SURROUNDINGS , EVAPORATION OF WATER AND I SAID EVAPORATION OF CRYSTALS ??? AND WHERE IT SAID WHY YOU CANNOT MEASURE IT DIRECTLY I SAID BECAUSE WE CANNOT USE A CALORIMETER?? ARE THESE CORRECT AND FOR THE ENTHALPY CALCULATION I GOT A NEGATIVE NUMBER BECAUSE I TAKE AWAYED THEM?
guys how many marks will i lose?/

Reply 44

Original post by 5 star

hi guys for the crystal question i describe how it is formed will they at leat give me some marks i said filter leave crystals to dry , leave them to cool? will i get at least 1 mark or 2?? for the three eeasons I PUT LOSS OF HEAT TO SURROUNDINGS , EVAPORATION OF WATER AND I SAID EVAPORATION OF CRYSTALS ??? AND WHERE IT SAID WHY YOU CANNOT MEASURE IT DIRECTLY I SAID BECAUSE WE CANNOT USE A CALORIMETER?? ARE THESE CORRECT AND FOR THE ENTHALPY CALCULATION I GOT A NEGATIVE NUMBER BECAUSE I TAKE AWAYED THEM?

I can't see you getting any marks for your description of making crystals because you're talking about a completely different experiment and it actually comes under an entirely different topic in Unit 1.

For the can't measure it directly one, I said it was because it was decomposition, so heat would have to be supplied for the reaction to take place so the thermometer reading would have to go up, but it's endothermic so difficult to actually determine the correct amount of energy that was actually absorbed. :dontknow:

Reply 45

ohhhhhhh OK HOW ABOUT MY THREE THINGS ABOUT BEING DIFFERENT FROM DATA BOOKS BY THE WAY DID YOU GET FOR THE CALCULATION OF ENTHALPY???????

Reply 46

Original post by 5 star

ohhhhhhh OK HOW ABOUT MY THREE THINGS ABOUT BEING DIFFERENT FROM DATA BOOKS BY THE WAY DID YOU GET FOR THE CALCULATION OF ENTHALPY???????

I dont know, your points seem fair, I talked about heat to the surroundings, an incomplete reaction and heat gain. I don't know what the mark scheme would accept tbh.

And I got +77, it was supposed to be reactants-products.

Also, you can turn off caps lock.

Reply 47

by the way did you get 1.74 for the concentration?? and did you put 750?? and did you put them in a fume cupboard?

Reply 48

5araol

So people did u find it hard or easy compared to past papers from 2009-2011?

Reply 49

for the question about why hydrogen cannot be detected did you put the c-h bond enthalopy is high and that the un light is less and this will cause not to detect the hydrogen?

Reply 50

Red_Dragon123

That was an easy paper but I made some STUPID rookie mistakes on there.

For the maximum yield of MgCl2 I wrote 1.82 grams? I don't know why at the time I thought it was right but after alot of people saying it was 1.57 or something but I did do the moles of hydrogen as its a 1:1 ratio times molar mass :\.

I also got +77 for my answer on enthalpy change of reaction? some people said they got a -answer

And the Skeletal formula of 22 dimethylpropane I wrote 1,2 Dimethylpropane :\

And what did everyone get for the yield question at the end of the MC? I got 95%

I think I got a good B on that paper but dropped a few marks away from an A :frown:

(edited 12 years ago)

Reply 51

aneesz

For the experiment i briefly described calorimetry and the use of the equation Q=m*c*t ? Anyone done the same?

Reply 52

You guys are wrong it was not +77 its meaant to be -77 it shows that in my book

Reply 53

For the MCQ on concentration I got one of the smaller numbers, cos I remember they gave you the mass in mg, so you had to convert it to grams and then find out how much was in 1000cm^3, blah blah.

Haha it took me ages to work out the hydrogen one. But basically the UV light only provide enough energy for the homolytic fission of the Cl-Cl bond, not the C-H, so hydrogen and CH3 free radicals aren't formed in initiation. When they are eventually formed in propogation, the H immediately reacts with the Cl free radical to form HCl. I think.

Reply 54

5 star

You guys are wrong it was not +77 its meaant to be -77 it shows that in my book

Please explain.

Reply 55