Chemistry: Post your doubts here!

[strangerss]

If the question specify what to put, then add what they want.
Incase not, then make nearest to 0.5.

But it depends on the thermometer you have. If the smallest division is 1 degree, then 0.5.

Oh ok , so it doesn't depend on the type of the experiment? thanks a lot for the help.

 

[strangerss]

MS Word + Screenshot + MS Paint + Tinypic.com

Why did you subtract 2x and not x from two moles of p , because the molar ratio between Q and p is the same so what ever was lost from P ,exactly forms Q , so that's why we shouldn't take x??

 

[19islandprincess96]

Has anyone done paper 5 of chem may June 09?
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s09_qp_5.pdf
Question 2?
I think I did something wrong in it.
Any suggestions?
Is that how we are supposed to do it?

 

[A star]

umm i guess the Cl- from the 1st mess of a molecule ( ) gets SUBSTITUTED by the whole mess of an anion ( ) from the 2nd molecule and HCl is formed as a result

hmm nice try but u make it sound like the bond formed is a ionic bond not a covalent. good use of the word messy though xD

 

[unseen95]

umm i guess the Cl- from the 1st mess of a molecule ( ) gets SUBSTITUTED by the whole mess of an anion ( ) from the 2nd molecule and HCl is formed as a result

thank you

 

[daredevil]

hmm nice try but u make it sound like the bond formed is a ionic bond not a covalent. good use of the word messy though xD

ummm see the compounds are converted into ions sort of... think about it ....
e.g. the first compound is turned into CH3CH2CO+ ion and Cl- ion ..... there are other reactions too where that sort of stuff happens u know like the reaction between carboxylic acid and metals... its simply like a simple acid + metal reaction instead there is a carboxylic acidd instead of a simple UN-messy one

and thanks for the compliment but that's just my suppressed inner creative self trying to stick its head out of the deep dark ocean that is called A levels

 

[daredevil]

thank you

no problem

 

[hassankhan]

Can someone explain this...
Q;Copper forms two chlorides CuCl and CuCl2
When copper is reacted directly with chlorine, only CuCl2 is formed. Suggest an explaination?

 

[iKhaled]

Can someone explain this...
Q;Copper forms two chlorides CuCl and CuCl2
When copper is reacted directly with chlorine, only CuCl2 is formed. Suggest an explaination?

because chlorine is a strong oxidizing agent so it will be strongly reduced by 2 electrons instead of one. As you go down the halogen group the element becomes less strongly as an oxidising agent and more strong as a reducing agent

 

[PhyZac]

Can someone explain this...
Q;Copper forms two chlorides CuCl and CuCl2
When copper is reacted directly with chlorine, only CuCl2 is formed. Suggest an explaination?

The lattice energy of CuCl2 is more negative than CuCl, (that is more exothermic) therefore more energy is released, therefore more stable and therefore more readily forms.

Sorry for using "therefore" alot!

 

[aalmuhannadi]

Can anyone help me with this? please? OCT/Nov 04 q13

I think it's D because NaOH is the strongest base out of the 4 given and so will be more strongly ionised in solution (equilibrium of ion dissociation is more likely to be to the right side rather than left) and so it would give a more accurate end-point than the rest, not sure if my reasoning is correct though if anyone would care to correct me?

 

[A star]

its better to leave mcqs for later you know

 

[PANDA-]

its better to leave mcqs for later you know

That's what I'm doing, didn't touch an mcq so far... Since there'll be about 1 month for those.

 

[megamind]

1)can any one tell me the mechanism of seperation whether adsorbtion or partionin HPLC
2) the stationery phase in HPLC
please?

 

[Ashique]

Has anyone done paper 5 of chem may June 09?
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_5.pdf
Question 2?
I think I did something wrong in it.
Any suggestions?
Is that how we are supposed to do it?

I got the same results. What did you do in the graph question? What did you plot in the x- and the y-axis? And what is the shape? I plotted solubility against temperature which, according to the mark scheme, is correct. But I seem to be getting a curve, aand the ms and the er rejects that. The questions also asks us to extrapolate the two lines, so they have to be straight lines. So what did you do?

 

[iKhaled]

I got the same results. What did you do in the graph question? What did you plot in the x- and the y-axis? And what is the shape? I plotted solubility against temperature which, according to the mark scheme, is correct. But I seem to be getting a curve, aand the ms and the er rejects that. The questions also asks us to extrapolate the two lines, so they have to be straight lines. So what did you do?

i am stuck in this question 2..i would appreciate it if someone can draw the graph and show it...

 

[daredevil]

urrgghh anyone pls tell me the best way to revise chemistry
if i do the past papers of only my variant i.e. variant 2 do u think i have it covered that way??
its just that a levels never seems like its fully prepared u know... like even at the last moment there's always this one thing left... this onw thing that u don't know .... if u know wat i mean.... i mean sure i m giving them the first time but i am already starting to get this feeling u know and even wen i asked around everyone said the same thing... so plz help me out on some tips here.... preferably on paper 2 at the moment. thanks
and Best of Luck all of u. Remember me and everyone else in your prayers

 

[PhyZac]

urrgghh anyone pls tell me the best way to revise chemistry
if i do the past papers of only my variant i.e. variant 2 do u think i have it covered that way??
its just that a levels never seems like its fully prepared u know... like even at the last moment there's always this one thing left... this onw thing that u don't know .... if u know wat i mean.... i mean sure i m giving them the first time but i am already starting to get this feeling u know and even wen i asked around everyone said the same thing... so plz help me out on some tips here.... preferably on paper 2 at the moment. thanks
and Best of Luck all of u. Remember me and everyone else in your prayers

What I would would is.

Do papers which I dint solve a couple per day, and read one of the three sections daily.

Sections are, Organic, InOrganic, Physical.

And byheart the organic route!

EDIT: Good luck with next week, May Allah S.W.T make it easy for you.

 

[littlecloud11]

1)can any one tell me the mechanism of seperation whether adsorbtion or partionin HPLC
2) the stationery phase in HPLC
please?

I'm not sure what you're asking by your first question but HPLC uses partitioning as a seperation technique and the stationary phase is a non-volatile liquid, usually long chain hydrocarbons.

 

[daredevil]

What I would would is.

Do papers which I dint solve a couple per day, and read one of the three sections daily.

Sections are, Organic, InOrganic, Physical.

And byheart the organic route!

EDIT: Good luck with next week, May Allah S.W.T make it easy for you.

ooo thankuu I have actually done the revision thingy but yeah i think i'll do the one section a day but according to my schedule i only have till friday to do aall my chem bcz need to leave 3 days of prep for maths too... -.- all of em lined up as they r in this horrible datesheet :O
anyways thanks for the tip... and wat do u think about the variants parrt? like should i do only my variant then wil it b enough? (although i know its never enough) but still hav i got my bases covered with that?
and one more thing if u have any kind of like worksheet or fill in the blanks kind of thing for the Organic OR INORGANIC equations will u post it? pwettty please?? ^_^ *desperate calls*