Chemistry Doubts: IGCSE Paper 3

[Jspake]

Please help me with qn 6 (a) http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w06_ms_3.pdf
I found the no. of moles as 0.75 (Cu), 0.75 (Fe) & 0.15 (S). I have no idea of how to find the simplest mole ratio..

 

[ThatReallyReallyWeirdDude]

Please help me with qn 6 (a) http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w06_ms_3.pdf
I found the no. of moles as 0.75 (Cu), 0.75 (Fe) & 0.15 (S). I have no idea of how to find the simplest mole ratio..

It says the ore only contains sulphur, iron and copper and by law of conservation of mass, the masses of Fe, S and Cu should add up to total mass
So mass of S = 13.8-4.8-4.2=4.8g
Next we find the number of moles each mass contains. (Here's a revision of formulas: http://www.xtremepapers.com/community/threads/chemistry-paper-3-calculations.16660/#post-289840)
So no. of moles = Mass/Mass of one mole.
Cu: No. of moles = 4.8/63.5=~0.0755
Fe: No. of moles =4.2/56=0.075
S: No. of moles = 4.8/32= 0.15
So the ratio of Cu:Fe:S is 0.075:0.075:0.15
We want this to be in whole numbers, the easiest way is to divide them all by the smallest number which is 0.075
so 0.075:0.075:0.15 all divided by 0.075 ->1:1:2
So the empirical formula is CuFeS2

 

[Jspake]

ohh man.. watz wrng wid me.. I used 0.75 instead of 0.075 & divided by the smallest number (0.15).. Thanks anywayz!

 

[Maz]

Check that :
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w11_ms_31.pdf Question 6 Part b(ii) .

I see. So, the OH part of the water is taken out from the ethanoic acid part and H from the ethanol part.

 

[ThatReallyReallyWeirdDude]

I see. So, the OH part of the water is taken out from the ethanoic acid part and H from the ethanol part.

OH is from the ethanol and H is from the ethanoic acid.
Carboxylic Acid group: -COO|H|
Alcohol (Hydroxyl) group: -OH
CH3CH2OH+CH3COOH->CH3COOCH3CH2+H2O (Ethyl Ethanoate)

 

[JOEJOE]

yah to make esters

Ester = Alkyl Alkanoate

Alkyl is always from the alchohol
Alkanoate is always from the acid!!!!

 

[ThatReallyReallyWeirdDude]

yah to make esters

Ester = Alkyl Alkanoate

Alkyl is always from the alchohol
Alkanoate is always from the acid!!!!

Any -anoate is the salt of an acid, so you can automatically know what's from the acid and what's from alkali even if you forget.
Sodium Ethanoate -> Ethanoate from Ethanoic Acid
Methyl Nonanoate -> Nonanoate from Nonanoic Acid, Methyl thus from Methanol.

 

[Z.A.M]

Joke if u understand Urdu just to chill
Methyl methanoate
Methyl nay metha kyun nahi kahya
Answer methyl ko diabetes hai
Just a joke guys

 

[JOEJOE]

Nylon = diamide + diacid

Terylene = Diacid + diol

Protein = aminoacid + aminoacid

Fats are esters

and starch is glucose molecules... just remove H and OH and then put a bracket and "n" down for all of these... hope this helped

 

[Moi]

Plz someone explain to me how do solve question 4 d of summer 05
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s05_qp_3.pdf

 

[JOEJOE]

Find the no of moles... Caso4 = 79.1/13 = 0.58
for H2O = 20.9/18 = 1.16

For the ratio to be 1:1 u have to divide by the smallest number so CaSo4 = 0.58/0.58
H2O = 1.16/0.58(smallest no)
so ratio is 1 : 2
CaSo4 H2O

 

[Moi]

Find the no of moles... Caso4 = 79.1/13 = 0.58
for H2O = 20.9/18 = 1.16

For the ratio to be 1:1 u have to divide by the smallest number so CaSo4 = 0.58/0.58
H2O = 1.16/0.58(smallest no)
so ratio is 1 : 2
CaSo4 H2O

THANKYOU !! Me and my friend spent the last 15 minuets trying to solve it !!
THANKYOUUUUUU

 

[JOEJOE]

ur welcome

 

[Beedo]

How to draw a labelled diagram of an alloy for example brass

 

[Maz]

How to draw a labelled diagram of an alloy for example brass

I hope you understand. Ignore the empty spaces in between.

 

[kanishk]

help i always get stuck in these
b) The structure of a typical protein is drawn below.
(it was just a picture of an amide linkage)
(ii) Draw the structural formula of a man-made polymer with the same linkage.

 

[Maz]

help i always get stuck in these
b) The structure of a typical protein is drawn below.
(it was just a picture of an amide linkage)
(ii) Draw the structural formula of a man-made polymer with the same linkage.

Draw the structure of nylon, since it has the same amide linkage.
-CO-[]-CO-NH-[|]-NH-CO-[]-CO-

[] is one box, [|] is a another box.

 

[kanishk]

Draw the structure of nylon, since it has the same amide linkage.
-CO-[]-CO-NH-[|]-NH-CO-[]-CO-

[] is one box, [|] is a another box.

wait but the the picture was NH-[]-CO-NH-[|]-CO-NH-{}-CO so isnt it like the same thing? can you clear this up im getting so confused with this....what make this and nylon different? i know that the link is the same but what else? sorry if i sound stupidly confused :/

 

[Maz]

wait but the the picture was NH-[]-CO-NH-[|]-CO-NH-{}-CO so isnt it like the same thing? can you clear this up im getting so confused with this....what make this and nylon different? i know that the link is the same but what else? sorry if i sound stupidly confused :/

Nope it's different.
Protien - NH-[|]-CO-,NH-[]-CO-.
Nylon- CO-[|]-CO-, -NH-[]-NH-.

Hope you understand.

 

[kanishk]

Nope it's different.
Protien - NH-[|]-CO-,NH-[]-CO-.
Nylon- CO-[|]-CO-, -NH-[]-NH-.

Hope you understand.

but why is it different? seems like the same monomers in both but its just reversing or something....ok to make it clearer can you tell me the monomers of both of those?