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[Skynox]

guys just a quick question for chem 31 the question abt the oxidant needed for ethanol ---> ethanoic acid conversion it cud be potassium manganate or dichromate. Was it necessary to mention the oxidation number?

Acidified potassium manganate (VII)
Acidified potassium dichromate (VI)
In a previous m.s they said MUST MENTION OXIDATION STATE

 

[IGSCE.Geek.]

people help me in this question:
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_w07_qp_1.pdf
question 15 why is it B but not A?

 

[Jspake]

it's name is cholesterol .. similar to alkanol "the ol" at the end .. the functional group of an alkanol is the hydroxide so the answer is B

Oh.. that was pretty easy.. thanks!

 

[Jspake]

Please help me with this question.. I understand that X is a metal and Y is a non-metal. But I don't really know how the formula was derived. If the valency of X is 2 and that of Y is 3.. the formula is supposed to be X3Y2 right?

 

[natsume hyuga]

according to the mark scheme (which i got from freeexampapers.com) the answer is A. Isnt it supposed to be C? This question is from the 2000 may june paper Chemistry

 

[natsume hyuga]

Please help me with this question.. I understand that X is a metal and Y is a non-metal. But I don't really know how the formula was derived. If the valency of X is 2 and that of Y is 3.. the formula is supposed to be X3Y2 right?

i dont think that 3 and 2 mean the valencies of the elements. Think abt it 2 atoms of X were deposited then there obviously has to be two atoms of X in the formula... here my weird analogy :s

 

[saroooor]

according to the mark scheme (which i got from freeexampapers.com) the answer is A. Isnt it supposed to be C? This question is from the 2000 may june paper Chemistry

Yeah Seriously , Does Water Has effect on the pH ??? isn't water neutral ?

 

[Razo513]

according to the mark scheme (which i got from freeexampapers.com) the answer is A. Isnt it supposed to be C? This question is from the 2000 may june paper Chemistry

it cant be A above 7 means alkali & alkali turns damp red litmus paper blue & not the oppostie :S.... can u plz attach the ms for june 2000 ill be thankful

 

[saroooor]

i dont think that 3 and 2 mean the valencies of the elements. Think abt it 2 atoms of X were deposited then there obviously has to be two atoms of X in the formula... here my weird analogy :s

Still didn't understand .......

 

[Razo513]

i dont think that 3 and 2 mean the valencies of the elements. Think abt it 2 atoms of X were deposited then there obviously has to be two atoms of X in the formula... here my weird analogy :s

if it was valency as u suggested then X^+2 & Y^-3 .. WHICH GIVES X3Y2... but it's the atoms not the valency .. they mentioned the NUMBER OF ATOMS deposited on each electrode & not the VALENCY of X or Y

 

[natsume hyuga]

it cant be A above 7 means alkali & alkali turns damp red litmus paper blue & not the oppostie :S.... can u plz attach the ms for june 2000 ill be thankful

 

[saroooor]

if it was valency as u suggested then X^+2 & Y^-3 .. WHICH GIVES X3Y2... but it's the atoms not the valency .. they mentioned the NUMBER OF ATOMS deposited on each electrode & not the VALENCY of X or Y

But , X(2) X(3) Shows it is a valency ??!! :S

 

[natsume hyuga]

But , X(2) X(3) Shows it is a valency ??!! :S

array bayya where did those brackets come from?

 

[saroooor]

array bayya where did those brackets come from?

I am showing that this is valency !!!

 

[Razo513]

i dont think that 3 and 2 mean the valencies of the elements. Think abt it 2 atoms of X were deposited then there obviously has to be two atoms of X in the formula... here my weird analogy :s

lsn to cut short when they say 2 atoms of X it means 2X and NOT X^2+ as well as when they say 3 atoms of Y it means 3Y and NOT Y^3- get it?

 

[natsume hyuga]

listen if ur confused, understand that the valency of y is 2, and the valency of x is 3. U swap them u get x2y3. This swapping helps u understand how many atoms are present for each element. therefore there are 2 atoms of x and 3 of y. read this slowly sentence by sentence and ull get it

 

[Razo513]

listen if ur confused, understand that the valency of y is 2, and the valency of x is 3. U swap them u get x2y3. This swapping helps u understand how many atoms are present for each element. therefore there are 2 atoms of x and 3 of y. read this slowly sentence by sentence and ull get it

what u wrote is kinda contradicting .. DO U THINK MY ANSWER MAKES SENSE which is when they say 2 atoms of X it means 2X and NOT X^2+ as well as when they say 3 atoms of Y it means 3Y and NOT Y^3- get it?

 

[Razo513]

according to the mark scheme (which i got from freeexampapers.com) the answer is A. Isnt it supposed to be C? This question is from the 2000 may june paper Chemistry

when so2 is dissolved in water as follows
SO2 + H2O --> H2SO3
it gives sulphurus acid which turns blue litmus paper red .. but what im not getting is why the pH above 7 !!

 

[natsume hyuga]

what u wrote is kinda contradicting .. DO U THINK MY ANSWER MAKES SENSE which is when they say 2 atoms of X it means 2X and NOT X^2+ as well as when they say 3 atoms of Y it means 3Y and NOT Y^3- get it?

okay wait, if u get x2y3 what does this mean? It means y has a valency of 2 and x has a valency of 3, no? No its not contradicting, im also saying that 2 atoms of x form and 3 for y.

 

[Razo513]

okay wait, if u get x2y3 what does this mean? It means y has a valency of 2 and x has a valency of 3, no? No its not contradicting, im also saying that 2 atoms of x form and 3 for y.

ahhhhhhhhhhh got it thx