A level chemistry paper help questions

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Bertybassett
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Hi I just did this past paper and I was wondering if someone could help me on some of the questions that I struggled with? Firstly, for 3d, how do you work this formula out? I thought a salt must contain a metal and non metal part? I really struggled with 6b, im confused as to what the question was even asking for - how do you work this out? For 3e, the mark scheme said that for one mark you had to say that the ratio of the conc of ch3ch2nh2 and ch3ch2nh3+ remained constant? what does this even mean and why?


Finally, I had some general questions - what is the actual meaning of a weak or strong base? Does it mean that in the reaction with water, the equilibrium lies far to the left and so partially dissociates?


Any help would be greatly appreciated https://pmt.physicsandmathstutor.com...%20A-level.pdf
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(Original post by Bertybassett)
Hi I just did this past paper and I was wondering if someone could help me on some of the questions that I struggled with? Firstly, for 3d, how do you work this formula out? I thought a salt must contain a metal and non metal part? I really struggled with 6b, im confused as to what the question was even asking for - how do you work this out? For 3e, the mark scheme said that for one mark you had to say that the ratio of the conc of ch3ch2nh2 and ch3ch2nh3+ remained constant? what does this even mean and why?


Finally, I had some general questions - what is the actual meaning of a weak or strong base? Does it mean that in the reaction with water, the equilibrium lies far to the left and so partially dissociates?


Any help would be greatly appreciated https://pmt.physicsandmathstutor.com...%20A-level.pdf
3D - the base ethylamine, in a buffered solution there is a mixture of the base and conjugate acid, or visa versa. In this case ethylamine solution would be mixed with something like ethylammonium chloride. As it produces the ethyl ammonium ion, it can produce ethylamine, or it can be produced from the protonation of ethylamine.

3E - essentially, as you change the conditions in a reaction the equilibrium shifts to oppose this. In pH, this means acception of releasing protons. When a buffer solution has a small amount of H+ or OH- added, the equilibrium moved to make sure proportional amounts of These ions are in solution with the other reacting species. Having equal proportions is maintaining the concentration ratio.

6B - is asking for you to identify the number and nature of peaks. Essentially asking you to identify the pieces that make up the molecule. I’ll let someone else help with that one, because I’m a little shaky on NMR!

General - yes, that’s exactly what it means
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username3249896
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An alkaline buffer containing ethylamine will contain ethylamine and a salt of ethylamine, e.g CH3CH2NH3Cl

When a small amount of HCl is added, the large amount of ethylamine present will react with H+:
CH3CH2NH2 + H+ -> CH3CH2NH3+

[CH3CH2NH3]/[CH3CH2NH3+] is nearly constant
CH3CH2NH2 + H2O <-> CH3CH2NH3+ + OH-
Kb = [BH+][OH-]/[B] where B = CH3CH2NH2
pH is kept constant so [OH-] is constant. Kb is constant too so [BH+]/[B] is constant. The equilibrium shifts to the right.

6(a) It is an alcohol.

4 singlet peaks -> 4 H environments
ratio 6:3:2:1

b) 2 H next to C=O
c) 3 H next to C=O
d) 2 CH3 in same environment

from (a) we know -OH is present
so X is CH3COCH2C(CH3)2OH
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Bertybassett
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(Original post by DrWilson173441)
3D - the base ethylamine, in a buffered solution there is a mixture of the base and conjugate acid, or visa versa. In this case ethylamine solution would be mixed with something like ethylammonium chloride. As it produces the ethyl ammonium ion, it can produce ethylamine, or it can be produced from the protonation of ethylamine.

3E - essentially, as you change the conditions in a reaction the equilibrium shifts to oppose this. In pH, this means acception of releasing protons. When a buffer solution has a small amount of H+ or OH- added, the equilibrium moved to make sure proportional amounts of These ions are in solution with the other reacting species. Having equal proportions is maintaining the concentration ratio.

6B - is asking for you to identify the number and nature of peaks. Essentially asking you to identify the pieces that make up the molecule. I’ll let someone else help with that one, because I’m a little shaky on NMR!

General - yes, that’s exactly what it means
thanks for the help!
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