WJEC CH1 Chemistry exam - 21/05/10 Watch

damagedyouth
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#21
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#21
i got that value too i agree with you guys though paper was different! with hardly no calculations?
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Zebra-Zahra
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#22
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#22
That exam was just one huge disaster for me!

I wrote so many stupid things, had ridiculous answers to calculations and, to top it all off, I ran out of time

There were more than few people in tears outside our exam hall

I wish I could go back and do it all over again!
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NcJns
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#23
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#23
what did you write for the environmental factors that manufacturers would need to consider?

I wrote that they need to consider the toxicity of the reactants used and the toxity of the product produced.
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Zebra-Zahra
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#24
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#24
(Original post by prince_of_paupers)
that exam was quite a bit more difficult than jan's - hopefully that will mean they lower the grade boundaries.
what did everyone put for the m/z value question in section A?
and also what was the answer to concentration of CO2 dissolved in water? (mol per dm3)
Oh ****, I think I forgot to go back and answer that one!
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Zebra-Zahra
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#25
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#25
What did everyone put for the atom economy? Was it 100%? That seems to be the most popular answer given in my school...
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Awakening
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#26
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#26
(Original post by prince_of_paupers)
that exam was quite a bit more difficult than jan's - hopefully that will mean they lower the grade boundaries.
what did everyone put for the m/z value question in section A?
and also what was the answer to concentration of CO2 dissolved in water? (mol per dm3)
for m/z i was clueless! i put 7+ because it was in group 7!
Anyone know what the answer was?
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Awakening
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#27
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#27
(Original post by Zebra-Zahra)
What did everyone put for the atom economy? Was it 100%? That seems to be the most popular answer given in my school...
Yup, got 100%

working out was 1/1 x 100 = 100%
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NcJns
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#28
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#28
How can we get hold of the paper, so we can have a look at it?
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damagedyouth
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#29
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#29
i got 100% too ;D
the concentration one, that was hard didn't even attempt it :|
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Zebra-Zahra
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#30
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#30
(Original post by NcJns)
How can we get hold of the paper, so we can have a look at it?
Maybe you could ask your teacher on Monday for a spare copy? I don't think there's anyway of getting it this weekend
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Zebra-Zahra
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#31
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#31
I think it might be a good(?) idea if we try to compile a list of the questions ourselves and then people can offer their answers if they want to?
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x_Melissa_x
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#32
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#32
(Original post by Zebra-Zahra)
I think it might be a good(?) idea if we try to compile a list of the questions ourselves and then people can offer their answers if they want to?
Yeah, that sounds like a good idea

I know that the first question asked about the number of protons and neutrons in Tritium...
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Rossshaw
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#33
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#33
Good luck people. I feel so down about it
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x_Melissa_x
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#34
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#34
(Original post by Rossshaw)
Good luck people. I feel so down about it
:console:

I think I'm beginning to accept the fact that I've failed!
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Rossshaw
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#35
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#35
(Original post by x_Melissa_x)
:console:

I think I'm beginning to accept the fact that I've failed!
By failed, I think I have like a C/D in it, which in all honesty is CRAP for me:mad:
I had an A in the mock last week!

I'm sure you will be ok
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planetconwy1
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#36
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#36
I went to my teacher afterwards to ask about the atom economy question, and he worked out the mass of those two molecules to be 116, and apparently it was 50%

Im really pleased about the paper other than that, and maybe the question about explosives for which i got about 4,000,000KJ or something
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dabeztstuff
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#37
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#37
(Original post by NcJns)
There was one question on enthalpy change involving ethene, did you get a positive value?
(It involved bond enthalpies and I had something like 3000 - 2000 = +1000 KJ mol-1 (roughly))
I figured the answer as follows:

Bond Average bond enthalpy at 298K and 1 atm.
/ kJ mol-1
H-H 436
H-O 463
H-C 412
C-C 348
C=C 612
C=O 743
O=O 498

CH2=CH2 +3 O=O => 2 O=C=O + 2 H-O-H

Bond breaking endothermic; bond making exothermic:

= +4(412) +(612) +3(498) -4(743) -4(463)

= +3754 -4824

= -1070kJ/mol

Unfortunately i got it wrong in the exam by using -2 factor instead of -4 on RHS. Seeing only 1 C=O and 1 O=H and getting a positive value. Damn its 4 marks too, i doubt ill get any method marks either.

The exam was very different compared to past papers... many found it short on time. Like no theory, all calculations and practical. Where was ionisation energies of the elements !!!
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abhijitnair
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#38
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#38
(Original post by prince_of_paupers)
that exam was quite a bit more difficult than jan's - hopefully that will mean they lower the grade boundaries.
what did everyone put for the m/z value question in section A?
and also what was the answer to concentration of CO2 dissolved in water? (mol per dm3)
i got 142 for the m/z
and 0.33 or something like that for the conc.
edit
i actually got 63 or something for the conc.
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abhijitnair
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#39
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#39
(Original post by dabeztstuff)
I figured the answer as follows:

Bond Average bond enthalpy at 298K and 1 atm.
/ kJ mol-1
H-H 436
H-O 463
H-C 412
C-C 348
C=C 612
C=O 743
O=O 498

CH2=CH2 +3 O=O => 2 O=C=O + 2 H2O

Bond breaking endothermic; bond making exothermic:

= +4(412) +(612) +3(498) -4(743) -4(463)

= +3754 -4824

= -1070kJ/mol

Unfortunately i got it wrong in the exam by using -2 factor instead of -4 on RHS. Seeing only 1 C=O and 1 O=H and getting a positive value. Damn its 4 marks too, i doubt ill get any method marks either.

The exam was very different compared to past papers... many found it short on time. Like no theory, all calculations and practical. Where was ionisation energies of the elements !!!
yessss i got that!!:woo:
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bex_1_2_1
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#40
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#40
What did people have for the 1st question on the 2nd page. You had to give 2 numbers? I messed it up i think
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