ALL CIE CHEMISTRY DOUBTS HERE !!

[Vin]

Does anybody have notes for mass- spectroscopy?
Like for eg, this question :

A sample of chlorine containing isotopes of mass numbers 35 and 37 was analysed in a
mass-spectrometer.
How many peaks corresponding to Cl₂⁺ were recorded?

A 2 B 3 C 4 D 5


Could anybody fill me in with some sense as to what the ques means in English? and everything in and around this topic? Thanks.

[Amii]

Does anybody have notes for mass- spectroscopy?
Like for eg, this question :

A sample of chlorine containing isotopes of mass numbers 35 and 37 was analysed in a
mass-spectrometer.
How many peaks corresponding to Cl₂⁺ were recorded?

A 2 B 3 C 4 D 5


Could anybody fill me in with some sense as to what the ques means in English? and everything in and around this topic? Thanks.

ans will be B
1 peak for Cl 35 and Cl 35
1 peak for Cl 35 and Cl 37
1 peak for Cl 37 and Cl 37

I am in a rush - have to get ready for tuitions - I will come back and try to make the explanation proper
Take care 

[Amelia]

Amii is right.

This topic is about (M) (M+2) (M+3) peaks. 

Both bromine and chlorine naturally occur as mixtures of 2 isotopes, with the relative abundances as shown :-

Chlorine -
            35 - Cl  relative abundance - 75.8%
            37-Cl   relative abundance - 22.4%
  approximate ratio - 3:1

Bromine -
         79 - Br relative abundance - 50.5%
         81 - Br relative abundance - 49.5%
approx. ratio - 1:1

The mass spectrum of a compound containing one of these elements should therefore show two molecular ions, one with an m/e value two mass units higher than the other. If the molecule contains two chlorine atome, we should expect to see three molecular ions, at m/e values of M, M+2, M+4. The ratio of the M/M+2 peak should reflect the natural abundances. (i.e 3:1 for chlorine, 1:1 for bromine).

You can just go through this : http://www.chemguide.co.uk/analysis/masspecmenu.html   

P.S - Sorry, esha. 

[Amii]

Amii is right.

This topic is about (M) (M+2) (M+3) peaks.  

Both bromine and chlorine naturally occur as mixtures of 2 isotopes, with the relative abundances as shown :-

Chlorine -
            35 - Cl  relative abundance - 75.8%
            37-Cl   relative abundance - 22.4%
  approximate ratio - 3:1

Bromine -
         79 - Br relative abundance - 50.5%
         81 - Br relative abundance - 49.5%
approx. ratio - 1:1

The mass spectrum of a compound containing one of these elements should therefore show two molecular ions, one with an m/e value two mass units higher than the other. If the molecule contains two chlorine atome, we should expect to see three molecular ions, at m/e values of M, M+2, M+4. The ratio of the M/M+2 peak should reflect the natural abundances. (i.e 3:1 for chlorine, 1:1 for bromine).

You can just go through this : http://www.chemguide.co.uk/analysis/masspecmenu.html  

P.S - Sorry, esha.  

LOL why sorry?    

Thank you so much  
I was getting late so I had to run  

[astarmathsandphysics]

The number of peaks is related to the number of isotopes
chlorine has two isotopes (I think) mass numbers 37 and 36 so Cl2 has three masses
2*37=74, 37+36=73,36+36=72
Hence three peaks, one for each mass

[Vin]

THANK YOUU SO MUCHH. I shall make sense out of it after my term exams. Thanks a lot, again!

[Amelia]

THANK YOUU SO MUCHH. I shall make sense out of it after my term exams. Thanks a lot, again!

You are welcome.

[Sue T]

i have an A2 ppr 5 ques
so we have this eqn:
CuCO3.Cu(OH)2.x H2O(s) ------> 2CuO(s) + CO2(g) + (x+1)H2O(g)
we're tryin 2 find x
wat i got is:
1) the mass of the basic copper carbonate (LHS) and;
2) loss in mass which is basically CO₂ and H₂O
there wer 2 expressions in the m.s. tht im supposed 2 use:
(221 + 18x); 44 + 18(x + 1);
ny has ny idea wat 2 do 2 find x ??
p.s. i hate paper 5.

[HUSH1994]

what do u need to know about isomers for AS and is knowledge about geometrical isomers needed?

[Amelia]

what do u need to know about isomers for AS and is knowledge about geometrical isomers needed?

According to the 2011 syllabus, you only need to know about the Optical Isomers.

Optical Isomers
When drawing a pair of optical isomers, candidates should indicate the three-dimensional structures
according to the convention used in the example below.
mirror plane

[Amelia]

i have an A2 ppr 5 ques
so we have this eqn:
CuCO3.Cu(OH)2.x H2O(s) ------> 2CuO(s) + CO2(g) + (x+1)H2O(g)
we're tryin 2 find x
wat i got is:
1) the mass of the basic copper carbonate (LHS) and;
2) loss in mass which is basically CO₂ and H₂O
there wer 2 expressions in the m.s. tht im supposed 2 use:
(221 + 18x); 44 + 18(x + 1);
ny has ny idea wat 2 do 2 find x ??
p.s. i hate paper 5.

eg :- mass of empty boiling-tube - 10.32g
mass of boiling-tube and basic carbonate before heating - 11.19g
mass of boiling-tube and residue after heating - 10.92 g.

After the heating the CO2 and H2O boil away and only CuO remains.
(11.19 - 10.92 g)(mol / 159.09 g) = 1.70e-3 mol rxn

(1.70e-3 mol)(221.1138 + 18.0148x) = 11.19 - 10.32 g
x = 16 (rounding to 2 s.d.)

P.S - I hope to be right. 

[Sue T]

  ummm... im sorry - i dont seem to get the working
IF there is no bother - pls elaborate just a lil bit more - im sure im jus missin smthin somewere
please and thank you 

[Amelia]

After the heating the CO2 and H2O boil away and only CuO remains.
(11.19 - 10.92 g)(mol / 159.09 g) = 1.70e-3 mol rxn

11.19 - 10.92 = 0.27g (mass of residue)

CuO - (63.546+16)x2

Find the moles.
The moles of the residue - 0.87/((63.546+16)x2) = 1.70e-3 mol rxn



Moles x RMM = Mass.
Therefore, use this eqn. to find X.
(1.70e-3 mol)(221.1138 + 18.0148x) = 11.19 - 10.32 g

[Sue T]

got it  thank you - sorry 4 th trouble 

[thecandydoll]

Heyy!
I need resources and help in Chemistry P5  Got no idea.No IDEA how to attempt this paper.