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Offline AN10

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chem question
« on: September 12, 2009, 10:34:40 am »
white phosphorus reacts with dilute aq. solutions of copper (II) sulfate to deposit metallic copper and produce a strongly alkaline sol.
In an experiment to investigate this reaction, 0.31g of white phosphorus reacted in excess aq. copper sulfate giving 1.6g of metallic copper.

(i) Calculate the new oxidation number of the phosphorus after the reaction.

(ii) In the reaction, the phosphorus forms an acid HPOn, what is the value of n.
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nid404

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Re: chem question
« Reply #1 on: September 12, 2009, 10:51:57 am »
(i) Ideally it should be +2...but i'm not very confident..think it's two cuz copper will accept two electron from phosphorous to become metal
(ii) H should also be having a subscrip...i've heard of nothing like this...plz check again

what is the answer though?
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Offline AN10

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Re: chem question
« Reply #2 on: September 12, 2009, 10:58:34 am »
i checked there is no subscript of H....n i dont know da answer....Thanks anywayz!...By the way do u hav any idea wht will be da equation for this reaction?
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nid404

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Re: chem question
« Reply #3 on: September 12, 2009, 11:07:39 am »
nope the question is strange....i don't know how there's an alkaline solution being formed in the first place....I'll find out anyways
if the question is correct, then it's pretty unusual
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nid404

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Re: chem question
« Reply #4 on: September 13, 2009, 04:50:23 am »
okay here you go...very strange reaction...

A Piece of ordinary phosphorus when placed in a solution of copper sulphate becomes covered with a black film of copper phosphide and then with a firm coating of bright metallic copper. The black phosphide is always found between the phosphorus and the copper.
check the pdf....i didn't get the head and tail of this reaction...a little new for me....
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Q80BOY

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Re: chem question
« Reply #5 on: September 15, 2009, 01:26:05 pm »
guys i have a chem question .. i didnt want to open a new thread just for one question .. plz help !! :)

its about Molecular formula ..

Q. An organic compound containing only carbon, hydrogen and oxygen was found to have 62.07% carbon and 10.33% hydrogen.
What is its molecular formula if Mr= 58.0?

%s confuse me !! :(
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Offline Ghost Of Highbury

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Re: chem question
« Reply #6 on: September 15, 2009, 01:32:26 pm »
i am getting C6H12O2
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Q80BOY

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Re: chem question
« Reply #7 on: September 15, 2009, 01:43:16 pm »
Thanks adi ..

can u guide me on how u did it plz ..

thanks !! :)
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Offline Ghost Of Highbury

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Re: chem question
« Reply #8 on: September 15, 2009, 01:47:38 pm »
Quote from: Q80BOY on September 15, 2009, 01:43:16 pm
Thanks adi ..

can u guide me on how u did it plz ..

thanks !! :)


.this how i did it...

                      C              H             O

MASS/100g    62.07        10.33       27.6

MOL. MASS      12              1           16

M/MM           5.1725         10.33      1.725

m/mm/1.725     3                6           1

            emp. formula - C3H6O

Mr = 58

total mass of C + H + O = 58
58/58 = 1

« Last Edit: September 15, 2009, 02:07:34 pm by eddie_adi619 »
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Q80BOY

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Re: chem question
« Reply #9 on: September 15, 2009, 01:53:17 pm »
ooooh .. so its the same but we just remove the %s :P

Thanks a lot adi !! (u will do gr8 in ur nov exams and AS !! ;))
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Offline Ghost Of Highbury

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Re: chem question
« Reply #10 on: September 15, 2009, 01:59:26 pm »
Quote from: Q80BOY on September 15, 2009, 01:53:17 pm
ooooh .. so its the same but we just remove the %s :P

Thanks a lot adi !! (u will do gr8 in ur nov exams and AS !! ;))
arre..thanks man!....hope i do...!
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Offline Ghost Of Highbury

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Re: chem question
« Reply #11 on: September 15, 2009, 02:00:47 pm »
i thought C6H12O2 didnt exist

its butyl acetate ohh!!

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nid404

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Re: chem question
« Reply #12 on: September 15, 2009, 02:02:58 pm »
I guess the molecular formula remains as C3H6O.
This is the empirical formula with mass=58
Since molecular formula has mass 58, the empirical formula is the molecular formula.
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Offline Ghost Of Highbury

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Re: chem question
« Reply #13 on: September 15, 2009, 02:05:45 pm »
Quote from: nid404 on September 15, 2009, 02:02:58 pm
I guess the molecular formula remains as C3H6O.
This is the empirical formula with mass=58
Since molecular formula has mass 58, the empirical formula is the molecular formula.

ohh..yaah...true..
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Q80BOY

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Re: chem question
« Reply #14 on: September 15, 2009, 02:07:08 pm »
By the way adi,

the EF is C3H6O

for the total mass, shouldnt we add up 3 carbons and 6 hydrogens etc. ?  :-\

(is that what nid and u decided on just now? :P)

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