AQA Chemistry Paper 2 AS Level 2016 Unofficial Mark Scheme

Original post by Splaffie

an isomer ALWAYS has the same molecular formula, they had the same mr but a different molecular formula

They had the same molecular formula, I even counted in the exam just to make sure

Reply 221

GabbytheGreek_48

11

Original post by Splaffie

an isomer ALWAYS has the same molecular formula, they had the same mr but a different molecular formula

they were both only made of carbon hydrogen and oxygen and to hav the same mr would hav to b in the same amount with each which meand they would hav the same molecular formula ?

Reply 222

Original post by neon_reaper

They had the same molecular formula, I even counted in the exam just to make sure

they had the same relative molecular mass but not the same chemical formula, butane has no oxygen and the others did so they are not isomers as soon as you consider that

Reply 223

Original post by Splaffie

they had the same relative molecular mass but not the same chemical formula, butane has no oxygen and the others did so they are not isomers as soon as you consider that

There were 3 molecules, 2 of them were isomers and the third was butane and the question was talking about the two that weren't butane.

Reply 224

marcobruni98

13

Original post by Splaffie

an isomer ALWAYS has the same molecular formula, they had the same mr but a different molecular formula, different molecules can have the same mr, for example c2h6 and h2c=o have the exact same mr but they are definitely not isomers

Are you sure they had different molecular formulae? I counted the number of atoms of each element and got the same number for each

Reply 225

Original post by neon_reaper

There were 3 molecules, 2 of them were isomers and the third was butane and the question was talking about the two that weren't butane.

pretty sure it was all 3 since butane has the same mr as propan-1-ol

Reply 226

What did everyone get for the last multiple choice question?

Reply 227

marcobruni98

13

Original post by Splaffie

pretty sure it was all 3 since butane has the same mr as propan-1-ol

Ahhhh no butane has no oxygen atoms so it is not an isomer

Reply 228

Original post by marcobruni98

Ahhhh no butane has no oxygen atoms so it is not an isomer

propanal and propanol are isomers, butane isnt, but they all had the same mr, the question was talking about why all 3 cant be determined by mass spectrometry and its because they all had the same mr

Reply 229

Original post by Al_YG

What did everyone get for the last multiple choice question?

C if it was the one about pressure and argon

Reply 230

Original post by Splaffie

C if it was the one about pressure and argon

Part C had the same increase in moles for Argon and had less of an increase in temperature? Do had a higher increase in temp for the same increase in moles (0.5)

Reply 231

Original post by Al_YG

What did everyone get for the last multiple choice question?

It was D. There was a relatively quick way to do it which was change PV = nRT into P=nT/V (R is a constant so you can ignore it). You could then sub in 1 for V because volume was a constant, then you could just keep changing the moles, temperature and volume as needed

Reply 232

D not Do apologies...

Reply 233

Original post by Splaffie

pretty sure it was all 3 since butane has the same mr as propan-1-ol

I'm pretty sure it was just the first two (what was it, propanal and prop-2-en-1-ol?) but I could be wrong, butane definitely wasn't an isomer though.

Reply 234

Original post by neon_reaper

It was D. There was a relatively quick way to do it which was change PV = nRT into P=nT/V (R is a constant so you can ignore it). You could then sub in 1 for V because volume was a constant, then you could just keep changing the moles, temperature and volume as needed

p is directionally proportional to both n and t, so multiply t by 1.5 and it came to 195 which was the highest value for all of them

for d the temperature change was 280, but a decrease of 0.5 moles gave you a value of 140

(edited 7 years ago)

Reply 235

Original post by neon_reaper

I'm pretty sure it was just the first two (what was it, propanal and prop-2-en-1-ol?) but I could be wrong, butane definitely wasn't an isomer though.

it was propanal prop-2-en-1-ol and butane

(edited 7 years ago)

Reply 236

Original post by neon_reaper

It was D. There was a relatively quick way to do it which was change PV = nRT into P=nT/V (R is a constant so you can ignore it). You could then sub in 1 for V because volume was a constant, then you could just keep changing the moles, temperature and volume as needed

There was an even quicker way which was to see the huge increase in temp for D and compare it with B's answer for one mole...lol D was the answer therefore.. what about the second to last. Sorry for bragging but no-one has answered all 15 multiple choices (only the first 12).

Reply 237