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CHEM1 15 May 2012 AQA OFFICIAL POST EXAM

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Reply 100

Jambone2

The isotope one was

85(2.5 * (100/3.5)) + 87(1 * (100/3.5))/100 = 85.57, so 85.6 :smile:

Yeah, I went all mathematical on it's ass.

That balancing equation one was an utter motherbitch.

(edited 11 years ago)

Reply 101

noobslayer

Original post by mobes

what did u put for y x and y have the same boiling point? i put they both have the same functional group...

They had different functional groups. One had a double C=C bond, one was an alkane. It's because they had very similar Mr values and chain lengths, which is what decides the bpt as it determines the amount of Van der Waals

Reply 102

Sunnyk1

the answer was

H3BO3+3naoh> NA3BO3+3h2O

Reply 103

DisturbingKand0R

Original post by SuziieB

2.5 times more than 87.

you may be right actually, what raw mark do you think you'll need for full ums

Reply 104

noobslayer

Original post by thetransitionary

Yeah it was 5000

lol bitches be getting me worried

Reply 105

Scienceisgood

Original post by Jambone2

The isotope one was

85(2.5 * (100/3.5)) + 87(1 * (100/3.5))/100 = 85.57, so 85.6 :smile:

Yeah, I went all mathematical on it's ass.

That balancing equation one was an utter motherbitch.

Nope, it was 86.4
I done it with 20 and 50.
I then done with 40 and 100
And then something else

Always got the answer 86.4

Reply 106

DisturbingKand0R

Original post by Sunnyk1

the answer was

H3BO3+3naoh> NA3BO3+3h2O

boron has a valancy of 3, it can't make that many bonds

Reply 107

Sunnyk1

the correct answer to that is 85.6

Reply 108

noobslayer

Original post by Scienceisgood

Nope, it was 86.4
I done it with 20 and 50.
I then done with 40 and 100
And then something else

Always got the answer 86.4

that would mean that there was more of the 87 mass isotope, it said there was 2.5x the amount of 85 than 87? so it must be closer to 85 on avg?

Reply 109

Jambone2

Original post by Scienceisgood

Nope, it was 86.4
I done it with 20 and 50.
I then done with 40 and 100
And then something else

Always got the answer 86.4

Not.physically.possible. The 85 was more abundant...

Reply 110

143143143

The correct answer to the functional group was:

https://upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Cyclobutane2.svg/325px-Cyclobutane2.svg.png

Do you think they would they accept:

http://tinyurl.com/cuhptdo

Still has same formula 'an all.

(Whoops, there's an extra hydrogen on the last carbon I forgot to draw. Would they still accept?)

(edited 11 years ago)

Reply 111

Sunnyk1

nah i think your incorrect, im an A2 student wh resat it, and H has 1+ ion and there was 3, with 3 Bo3 so it would be similar to nabo3

(edited 11 years ago)

Reply 112

Lily.K

Original post by Ahmad*

it was

H3BO3 + 3NaOH---- Na3BO3 + 3H20

Do you mean H3BO3 + 3NaOH---- 3Na3BO3 + 3H2O?
I thought the formula for sodium borate was Na3BO3 as well, I made it up though, so not 100% sure.

Reply 113

DisturbingKand0R

Original post by Scienceisgood

Nope, it was 86.4
I done it with 20 and 50.
I then done with 40 and 100
And then something else

Always got the answer 86.4

either way the method seems to be the same, just a mistake in reading the question. Could still get method marks no matter who's right
But i have to say 50% of people got 86.4, 10% didn't have a clue and guessed
and 40% got 85.6, it's hard to call

Reply 114

noobslayer

Original post by Scienceisgood

Nope, it was 86.4
I done it with 20 and 50.
I then done with 40 and 100
And then something else

Always got the answer 86.4

you confused the 85 and 87 as being the wrong way round

Reply 115

DisturbingKand0R

Original post by noobslayer

that would mean that there was more of the 87 mass isotope, it said there was 2.5x the amount of 85 than 87? so it must be closer to 85 on avg?

no one is really sure what the actual question said

Reply 116

noobslayer

Original post by DisturbingKand0R

no one is really sure what the actual question said

I am it said the 85 isotope was 2.5 more abundant than the 87...

Reply 117

exclusive110

Im pretty sure it was 85.6 since the abundance for 85 was 2.5 times greater than 87, so at the end the value should be closer to 85.

For the PV=nRT did anyone get the mass around 2 grams or something like that?

Reply 118

Scienceisgood

Actually, sorry guys. I made a mistake in my 86.4 (not on paper, writing it here)

It actually was 85.6 (and I'm not just saying that), I think I remembered my first answer before correcting it. I did admit to myself it was a bit high when I first saw it. Sorry, I got 85.6 :wink: