A-level Chemistry Revision Squad!
Scroll to see replies
Hey Guys! This is the official thread for tomorrow's Chem Unit 1 Edexcel exam. Make sure to discuss the paper there after you are done. Of course, wait for like half an hour after you are done coz some people may still be doing it. Good Luck!! 
http://www.thestudentroom.co.uk/showthread.php?t=4101117&x=0&y=0#post65221487
http://www.thestudentroom.co.uk/showthread.php?t=4101117&x=0&y=0#post65221487
(edited 7 years ago)
Original post by Science_help
Lets see who gets this right.
No using google or textbook btw.
What temperature does diamond melt at ? nearest 100
No using google or textbook btw.
What temperature does diamond melt at ? nearest 100
I have an important question. Can someone sit the exam for me please?! 
Original post by Enderbat1999
guys question,
in mass spec why do we get different peaks for example Kr+1 and Kr+2
and where are they drew on the mass spec graph
in mass spec why do we get different peaks for example Kr+1 and Kr+2
and where are they drew on the mass spec graph
you get various ions if you provide more energy to the sample then its first ioninsation energy.
if kr+1 was m/z =84 on the graph, kr+2 would be 42, because x axis is is m/z, therefore if you have twice the charge the number halves
Original post by GracelovesNeuro
With the Hydroxides what are the test you do when its cloudy milky etc?? Quite confused and its not in the textbook.I'm referring to the part of the spec where it states "Students could test the solubility of Group 2 hydroxides by mixing solutions of soluble Group 2 salts with sodium hydroxide and record their results." vice versa for Sulfates.
From the reaction between unknown soluble group 2 salts and sodium hydroxide, you form a group 2 hydroxide (XCl2 + 2NaOH --> X(OH)2 + 2NaCl, where X is a group 2 element)
And to test whether the group 2 hydroxide is produced from the reaction above, you dip a red litmus paper into the solution and if hydroxide ions are present, the paper will turn blue.
The hydroxide ions make the solution alkaline hence you use the litmus paper.
(edited 7 years ago)
Original post by CERC
Ok, so i'm just going to type out what my revision guide says about this:
1) The M+1 peak is a small peak one m/e value above the M+ peak. It is caused by the presence of ONE Carbon-13 atom in the molecular ion.
2) A MAJOR peak at M+2 is caused by the presence of either Cl or Br atom in the molecule. Both Chlorine and Bromine have isotopes that differ by two mass units. Chlorine has 35 and 37 whilst Bromine has 79 and 81.
IMPORTANT: If the ration of the M+ peak to the M+2 peak is 3:1 i.e. the M+ peak is three times as abundant as the M+2 peak, then a chlorine atom is present.
However, the Bromine 79 and Bromine 81 have the same abundance, in a ration of 1:1. So, if the M+ peak has the same abundance as the M+2 peak then a Bromine atom is present in the molecule!
Really hope this helps you!
1) The M+1 peak is a small peak one m/e value above the M+ peak. It is caused by the presence of ONE Carbon-13 atom in the molecular ion.
2) A MAJOR peak at M+2 is caused by the presence of either Cl or Br atom in the molecule. Both Chlorine and Bromine have isotopes that differ by two mass units. Chlorine has 35 and 37 whilst Bromine has 79 and 81.
IMPORTANT: If the ration of the M+ peak to the M+2 peak is 3:1 i.e. the M+ peak is three times as abundant as the M+2 peak, then a chlorine atom is present.
However, the Bromine 79 and Bromine 81 have the same abundance, in a ration of 1:1. So, if the M+ peak has the same abundance as the M+2 peak then a Bromine atom is present in the molecule!
Really hope this helps you!
Yeah, that helped so much!!! Thank you
Original post by PlayerBB
Yeah, that helped so much!!! Thank you
Just so you know for edexcel you aren't expected to interpret mass specs that have m+1 m+2 peaks etc.
Original post by samb1234
Just so you know for edexcel you aren't expected to interpret mass specs that have m+1 m+2 peaks etc.
Really, well that's definitely great! But it was good to have an idea about them though
Posted from TSR Mobile
Why would there be a peak at 80 in mass spectrometry of Bromine? There are only two isotopes of bromine- 79 and 81 so why would there be peak at 80?
Original post by damian21kk
Why would there be a peak at 80 in mass spectrometry of Bromine? There are only two isotopes of bromine- 79 and 81 so why would there be peak at 80?
hard paper guys not good messed up on alot of the maths questions
Original post by Enderbat1999
hard paper guys not good messed up on alot of the maths questions
I thought it was easy except that question which doesn't make any sense.
Original post by damian21kk
Why would there be a peak at 80 in mass spectrometry of Bromine? There are only two isotopes of bromine- 79 and 81 so why would there be peak at 80?
Br2 with one Br79 one Br81 and a 2+ charge
Original post by damian21kk
Why would there be a peak at 80 in mass spectrometry of Bromine? There are only two isotopes of bromine- 79 and 81 so why would there be peak at 80?
I wrote that there is a Br2 molecule that is 79Br81Br so it adds up to 160. When it is being ionised it lost two electrons to form a 2+ ion and didn't fragment. So the m/z ratio is 160/2 which is 80
Hi guys am making a whattsapp group. please dm me. The whattsapp group is going to be for all chemistry examboards, as we all need to know the same things but just in different orders. PLease do DM me. thanks xx
Can someone please explain the highlighted question please? I looked into several textbooks couldn't find the answer to it.. It's for OCR B Salters course lol🙈
Posted from TSR Mobile
Original post by FemaleBo55
Can someone please explain the highlighted question please? I looked into several textbooks couldn't find the answer to it.. It's for OCR B Salters course lol🙈
Posted from TSR Mobile
Can someone please explain the highlighted question please? I looked into several textbooks couldn't find the answer to it.. It's for OCR B Salters course lol🙈
Posted from TSR Mobile
Partial pressures of the different gases?
Can someone please tell me how to calculate the enthalpy change of combustion and the enthalpy change of formation when given a table? I always get confused from which calculation of enthalpies do I need to take away the sum of products from the sum of the reactants!!!!
This is for OCR Chemistry A
This is for OCR Chemistry A
Original post by seph_muriel
Can someone please tell me how to calculate the enthalpy change of combustion and the enthalpy change of formation when given a table? I always get confused from which calculation of enthalpies do I need to take away the sum of products from the sum of the reactants!!!!
This is for OCR Chemistry A
This is for OCR Chemistry A
For combustion you do reactants take away products. I rememeber this using the acronym CRAP or CAP ( combustion reactant takeaway products) CRAP sticks in my head aha
Posted from TSR Mobile
Quick Reply
Related discussions
- TSR Study Together - STEM vs Humanities!
- GCSE Exam Discussions 2024
- A-level Chemistry Help
- A-level chemistry revision, taking notes and exam practise help and paper 3
- A- levels
- A level chemistry
- Where to revise for module 1 for OCR A chemistry?
- Im failing a-level chemistry! Help!
- Chemistry A-level
- Is SnapRevise for chemistry worth the cost ?
- when did u start revising for a levels?
- Chemistry A-level?
- Should i drop chemistry
- Learning techniques
- A- levels
- Revision for A level
- Revision tips for Year 12s? Biology, Chemistry, Maths.
- I've forgotten everything in A level chemistry
- Free revision/quizzez to improve my grades for A lvl Bio and Chem
- A level choice dilema!!!
Latest
Trending
Last reply 6 days ago
Im confused about this chemistry question, why does it form these productsTrending
Last reply 6 days ago
Im confused about this chemistry question, why does it form these products
