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AQA A-level Chemistry Autumn Exam 7405 P 1,2,3 6/13/19 Oct 2020 - Exam Discussion

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I thought it was to rinse the edges with distilled water. We've never reweighed the boat after taking the solid off. Always before :/

i think it’s actually one of those questions where there are two answers, you can either measure the mass again or you wash the weighing boat with distilled water to get any leftover salicylic acid, so i wouldn’t worry if you didn’t put reweigh

(edited 3 years ago)

Reply 181

nakamamgggd

I still dont know how the mass of aspirin is 6g. I got like 14 lmfao

i worked out mass from density, added it to the other mass and multiplied by 0.841. what am i doing wrong?

Reply 182

Yo...

Original post by nakamamgggd

I still dont know how the mass of aspirin is 6g. I got like 14 lmfao

i worked out mass from density, added it to the other mass and multiplied by 0.841. what am i doing wrong?

I got 13. something and was confident lmao

Reply 183

hamz.at

Original post by Yo...

I got 13. something and was confident lmao

i got 10.2 which would be 84 percent of 12.1/12.2

was 84.1 i think

Original post by nakamamgggd

I still dont know how the mass of aspirin is 6g. I got like 14 lmfao

i worked out mass from density, added it to the other mass and multiplied by 0.841. what am i doing wrong?

well you can't just add the masses, you have to work out which reagent is in excess then as it's a 1:1 ratio, you can work out the therotical maximum number of moles. Then when you have that you can multiply that by 0.841 to get the moles actually made then convert into grams to get your answer.

Reply 186

sxronnn

what did you guys get for the kc question the concentration of I think ? i got 0. something i just can't remember

Reply 187

random678

Original post by sxronnn

what did you guys get for the kc question the concentration of I think ? i got 0. something i just can't remember

0.0032 i think

Reply 188

sxronnn

Original post by random678

0.0032 i think

ohh ty yh i'm still not sure that answer isn't ringing any bells right now

Reply 189

random678

if anyone finds the unofficial mark scheme please linkk it here

Reply 190

sdfsdf7676

for the missing step in the experiment, i put fill to 100cm3 with deionised water, so u can calculate cincentration

Reply 191

hamzahkala

Original post by SpaceTravel

I essentially said that too

yh the chlorine is the main reason for higher reactivity because it pulls electron density towards itself and thus forms a partial positive charge in the carbon it is bonded to

Reply 192

hamzahkala

Original post by Harrybeld

the carbon-oxygen double bond was part of the amide structure I believe.

correct, the amine structure would not have C=O. an amide would have this so it was an amide

Reply 193

Anonymous17!

I was consumed because we were given mad of O2 but then CO2 and H2O, not C and H. At least not directly. I worked out the moles for CO2 and H2O based on their mr and mass and they weren’t equal so I gave up. I guess i should have done a 2:1 ratio. Idk. **** me, idc any more tbh. No way I’m going to get an A for chemistry and I’m going to fail maths as well. I don’t want to do the exam AGAIN in summer and resit but looks like I might have to :frown:

Reply 194

hamzahkala

Original post by Yo...

I got 13. something and was confident lmao

its a 1:1 ratio. about 6.6g is correct.

it was 84.1%

Original post by Harrybeld

Did anyone else get 6.61 grams for the mass of aspirin produced?

**** I rounded it to 6.60.

Reply 197

p.sbt

Total marks needed for an A:

2017: 204
2018: 198
2019: 206

What’s the maximum everyone thinks it could be this year? 210-215 maybe?

Reply 198

Anonymous17!

Original post by sxronnn

what did you guys get for the kc question the concentration of I think ? i got 0. something i just can't remember

I don’t even remember a question where we had to find the concentration of B. All I remember is the first question that said find the imitation rate of reaction and then one question that said find [M] (I got 0.275 or something). What was this question??