Chemistry: Post your doubts here!

[Amy Bloom]

People please help me here i dont get this one question from paper 2 seems quite simple

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s03_qp_2.pdf
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s03_ms_1 2 3 4 5 6.pdf
Q1 part C it says explain your answer. but i dont get the answer they gave in the mark scheme Why does the ratio have to be 3:1?

If you have a look at the relative abundances, that is,
H35Cl (line at m/e value 36) has relative abundance 90
H37Cl (line at m/e value 38 has relative abundance 30
Hence these show that 35Cl and 37Cl are in the ratio 3:1

 

[hmlahori]

If you have a look at the relative abundances, that is,
H35Cl (line at m/e value 36) has relative abundance 90
H37Cl (line at m/e value 38 has relative abundance 30
Hence these show thet 35Cl and 37Cl are in the ratio 3:1

well i get that part but how does that help in telling us that these are the peaks that will determine the proportions of the isotopes of chlorine
like how does the ratio 3:1 tell us that?

 

[Amy Bloom]

well i get that part but how does that help in telling us that these are the peaks that will determine the proportions of the isotopes of chlorine
like how does the ratio 3:1 tell us that?

I'm sorry i don't get what u r trying to say.

 

[hmlahori]

hello there.
Can anybody answer this:
A solution of vanadium (V) ions in 1 mol dm-3 H2SO4 slowly oxidises arsenic (III) oxide to arsenic (V) oxide according to the following (unbalanced) equation. Balance the equation.
As2O3 + VO2+ + H+ ---> As2O5 + VO2+ + H2O

Are you sure this equation is correct because i think the oxidation state of VO2+ will change as it oxidizes the As2O3 and so will be reduced itself?

 

[Amy Bloom]

Are you sure this equation is correct because i think the oxidation state of VO2+ will change as it oxidizes the As2O3 and so will be reduced itself?

Sorry while typing there's been some problem
on the reactants side the VO2^+ (the plus is superscript)

 

[Amy Bloom]

well i get that part but how does that help in telling us that these are the peaks that will determine the proportions of the isotopes of chlorine
like how does the ratio 3:1 tell us that?

Oh now i get it. it simply asks u how you arrived at 3:1. The explanation lies in the abundances.

 

[hmlahori]

Oh now i get it. it simply asks u how you arrived at 3:1. The explanation lies in the abundances.

Oh ok rite i read the question again and before i was reading it wrong or taking it in another sense but i get it now so first we'r supposed to come to the 3:1 ratio and then explain how we got it which is basically by taking in consideration the relative abundances. well thanks u put me on the rite track.

 

[Amy Bloom]

Oh ok rite i read the question again and before i was reading it wrong or taking it in another sense but i get it now so first we'r supposed to come to the 3:1 ratio and then explain how we got it which is basically by taking in consideration the relative abundances. well thanks u put me on the rite track.

u're most welcomed ^^

 

[hmlahori]

Sorry while typing there's been some problem
on the reactants side the VO2^+ (the plus is superscript)

im sorry i cant balance this if you could write the complete equation again and then i'll try

 

[gary221]

hey ppl, how do v get this ester in q 5 a)??
summer 2011 p22
thnk u..

 

[donor]

hey ppl, how do v get this ester in q 5 a)??
summer 2011 p22
thnk u..

we would esterify all the three alcohol groups with the stearic acid

 

[Amy Bloom]

Can anybody answer this question please???

 

[gary221]

we would esterify all the three alcohol groups with the stearic acid

n each of the alcohol grp shud be bonded with each othr??

 

[donor]

n each of the alcohol grp shud be bonded with each othr??

yes each alcohol group will attach to carboxylic acid group

 

[anshul]

can somebody please help me to work out the question on planning??
i'm finding it a real pain.
please help me!
pg 6 ex 2

 

[Jaf]

Can anybody answer this question please???

As2O3 + 4(VO2)^(+) + 4H+ à As2O5 + 4(VO)^(2+) + 2H2O​

​

 

[Amy Bloom]

yes each alcohol group will attach to carboxylic acid group

And form water molecules, depending on the number of OH bonding with H. don't forget its a condensation reaction.

 

[Amy Bloom]

As2O3 + 4(VO2)^(+) + 4H+ à As2O5 + 4(VO)^(2+) + 2H2O​

​

Thanks a lot pal!

 

[Soulgamer]

Guys, I think the marking scheme is wrong here. Check out Question 5.

The third box, the marking key says E only.
But wouldn't the ketone and aldeyde be reduced by H2(Hydrogen)
It should've been C,D and E.

 

[hmlahori]

Please someone explain these paper 2 questions!

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w09_qp_21.pdf
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w09_ms_21.pdf
Q 3 (a iii) the answer is that activation energy is too high thats why reaction does not take place but i dont get why and how it will be high
Q 3 (c) explain why the shape of the graph is like that shown in the mark scheme.......i dont get it at all!
Q 4 (a iii) Why cant there be another compound apart from A and D as written in the mark scheme? E can show position isomerism......cant it?