Higher Chemistry 2018-19 Watch

sadia_azhar
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Hi Everyone!

Welcome to the Higher Chemistry thread. This is a thread for those who are studying Higher Chemistry for the term of 2018/19. This thread can be used to ask questions, get help on any past paper questions you don't understand or anything related to higher chemistry!!!
Everyone is welcome to join
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dude101010
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someone plz help on this questiona mixture of potassium chloride and potassium carbonate is known to contain 0.1 mol chloride ions and 0.1mol of carbonate ions. how many mols of potassium ions are present?
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sadia_azhar
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(Original post by dude101010)
someone plz help on this questiona mixture of potassium chloride and potassium carbonate is known to contain 0.1 mol chloride ions and 0.1mol of carbonate ions. how many mols of potassium ions are present?
The answer is 0.3 moles because I’m potassium chloride the ratio of K:CL is 1:1 so if there is 0.1 moles of Cl there should be 0.1 mol of K

For potassium carbonate the ratio is 2:1 (formula is K2CO3) so if there is 0.1 mol of CO3 there must be 0.2 mol of K
Does that make sense?
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dude101010
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(Original post by sadia_azhar)
The answer is 0.3 moles because I’m potassium chloride the ratio of K:CL is 1:1 so if there is 0.1 moles of Cl there should be 0.1 mol of K

For potassium carbonate the ratio is 2:1 (formula is K2CO3) so if there is 0.1 mol of CO3 there must be 0.2 mol of K
Does that make sense?
thank you
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keitlenchips
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hey!!!! glad I found this thread! how is everyone finding the course? I was at first struggling but in a recent test, I only lost one mark so clearly I was doing something right! any of yall planning on doing adv/studying it at uni?
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sadia_azhar
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(Original post by keitlenchips)
hey!!!! glad I found this thread! how is everyone finding the course? I was at first struggling but in a recent test, I only lost one mark so clearly I was doing something right! any of yall planning on doing adv/studying it at uni?
Hii!

So far I’m finding the course pretty tough but hopefully things will get a bit easier when I get a bit more practice. I’m planning on doing Advanced higher chemistry as well, what about yourself?
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keitlenchips
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(Original post by sadia_azhar)
Hii!

So far I’m finding the course pretty tough but hopefully things will get a bit easier when I get a bit more practice. I’m planning on doing Advanced higher chemistry as well, what about yourself?
yup! I’m planning on doing advanced higher and then going on to studying at university ((I also want a phd in chem))

Redox is horrible, so much worse than national 5 so I’ve kinda sworn off inorganic chemistry because of it (a teacher at my school said his inorganic chemistry teacher only had 7 fingers)
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Labrador99
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How is everyone getting on? Ready for the chemistry prelim?
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keitlenchips
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(Original post by Labrador99)
How is everyone getting on? Ready for the chemistry prelim?
defo- worries about open ended questions bc of how challenging they can be but apart from that it should be all good
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purplesodium
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I'm terrible at open-ended questions - I always somehow manage to repeat the entire National 5 course without a hint of Higher content and end up getting 0 marks. They're so difficult to practise because marking schemes are so specific to the question's content and they aren't so much about structure as they are about knowledge . Guess I just have to work on the latter.
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Labrador99
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(Original post by keitlenchips)
defo- worries about open ended questions bc of how challenging they can be but apart from that it should be all good
Open ended questions are not that nice :no: My advice would be to skip them and come back to them at the end in the prelim/exam. The trick with them is figuring out what the underlying chemistry of the particular situation is...Once you've got that, write about it, and make sure that you apply it to whatever situation/context the question is based around.
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Lil Impulse
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Was doing a past paperquestion from 2018 Higher chemistry examName:  TerpeneQuestion.png
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Size:  60.2 KB. I circled the 5 carbon and 8 hydrogens to the left as an isoprene unit is C5H8. However in the marking instructions they do not circle C5H8. Could someone please explain this question to me as the marking instructions do not make any sense. Many thanks.
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sbneelu
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(Original post by Lil Impulse)
Was doing a past paperquestion from 2018 Higher chemistry examName:  TerpeneQuestion.png
Views: 5
Size:  60.2 KB. I circled the 5 carbon and 8 hydrogens to the left as an isoprene unit is C5H8. However in the marking instructions they do not circle C5H8. Could someone please explain this question to me as the marking instructions do not make any sense. Many thanks.


Isoprene is 2-methylbuta-1,3-diene, so it has a methyl group coming off its second carbon, and double bonds from its first and third carbons.

Name:  Screenshot 2019-01-10 at 8.13.26 pm.png
Views: 3
Size:  13.4 KBis valid because the double bonds are at carbons 1 and 3 if the main chain is from the CH2 at the top to the CH2 at the bottom right, with a methyl group coming off the second carbon.
Name:  Screenshot 2019-01-10 at 8.15.46 pm.png
Views: 3
Size:  13.5 KB is also a valid answer because while its double bonds aren't where you are expecting them to be, its bonding means that it was originally a unit of isoprene. You can tell because it has a chain of 4 carbon atoms with a methyl group coming off the second carbon. (I'm not 100% sure about if this is the way to actually do it but it's how I've been doing it and it seems to work so someone correct me if I'm wrong please.)

I'm not sure exactly what you mean by the left but I'm assuming you mean something like this:
Name:  Screenshot 2019-01-10 at 8.17.55 pm.png
Views: 3
Size:  13.4 KB
The problem with this one is that all five carbons are in one chain so it's pentadiene rather than butadiene with a methyl group, so it's not an isoprene unit.
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Lil Impulse
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(Original post by sbneelu)
Isoprene is 2-methylbuta-1,3-diene, so it has a methyl group coming off its second carbon, and double bonds from its first and third carbons.

Name:  Screenshot 2019-01-10 at 8.13.26 pm.png
Views: 3
Size:  13.4 KBis valid because the double bonds are at carbons 1 and 3 if the main chain is from the CH2 at the top to the CH2 at the bottom right, with a methyl group coming off the second carbon.
Name:  Screenshot 2019-01-10 at 8.15.46 pm.png
Views: 3
Size:  13.5 KB is also a valid answer because while its double bonds aren't where you are expecting them to be, its bonding means that it was originally a unit of isoprene. You can tell because it has a chain of 4 carbon atoms with a methyl group coming off the second carbon. (I'm not 100% sure about if this is the way to actually do it but it's how I've been doing it and it seems to work so someone correct me if I'm wrong please.)

I'm not sure exactly what you mean by the left but I'm assuming you mean something like this:
Name:  Screenshot 2019-01-10 at 8.17.55 pm.png
Views: 3
Size:  13.4 KB
The problem with this one is that all five carbons are in one chain so it's pentadiene rather than butadiene with a methyl group, so it's not an isoprene unit.
Thank you for explaining how to get the right answer so quickly. I did put the picture displayed at the bottom as my answer. Only thing I don't quite get is how the correct answer displayed at the top has 7 hydrogens when an isoprene unit has 8 hydrogens.
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sbneelu
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(Original post by Lil Impulse)
Thank you for explaining how to get the right answer so quickly. I did put the picture displayed at the bottom as my answer. Only thing I don't quite get is how the correct answer displayed at the top has 7 hydrogens when an isoprene unit has 8 hydrogens.
No problem!

Okay so an actual molecule of isoprene has 8 hydrogens but to combine multiple units of isoprene a C-H bond is removed and replaced with a C-C bond or if the isoprene unit is being bonded to something else a C-H bond is broken and the carbon bonds to something in the other molecule. When the C-H bond is broken the hydrogen atom is replaced with another isoprene unit/other molecule.
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Lil Impulse
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(Original post by sbneelu)
No problem!

Okay so an actual molecule of isoprene has 8 hydrogens but to combine multiple units of isoprene a C-H bond is removed and replaced with a C-C bond or if the isoprene unit is being bonded to something else a C-H bond is broken and the carbon bonds to something in the other molecule. When the C-H bond is broken the hydrogen atom is replaced with another isoprene unit/other molecule.
Think I understand it now. Thanks
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sbneelu
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(Original post by Lil Impulse)
Think I understand it now. Thanks
No problem!
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creo_scorpio
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Just did a chemical industry calculations test and pretty sure teacher could hear me muttering swear words under my breath...
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