Chemistry Doubts: IGCSE Paper 3

[ThatReallyReallyWeirdDude]

umm, is that complicated alcohol glycerol??

Well yeah I think that's given as an example.

 

[ThatReallyReallyWeirdDude]

Can someone please explain hydrolysis.. i'm clueless.. and its use in fats, amino acids.. etc. Please reply! I'm eating my book to get the concept..

http://www.xtremepapers.com/communi...y-revision-guide-according-to-syllabus.16647/
Page 98

 

[Tekno-M]

No, there's no bond between Cl and O, the bond should be between Cl and C. I think that's the only mistake you have.

 

[Tekno-M]

I think this is correct.

 

[Jspake]

I think this is correct.

Oh man.. i didn't think of that. Thanks a lot!

 

[Jspake]

http://www.xtremepapers.com/communi...y-revision-guide-according-to-syllabus.16647/
Page 98

It's till page 97.. I don't find anything abt hydrolysis

 

[ThatReallyReallyWeirdDude]

It's till page 97.. I don't find anything abt hydrolysis

Oh sorry, pg96
It's not a heading by itself, it's part of the Protein section and Fat section.

 

[JimmyCarter]

(d) Gypsum is hydrated calcium sulphate, CaSO4.xH2O. It contains 20.9% water by mass.
Calculate x.
Mr: CaSO4, 136; H2O, 18.
79.1 g of CaSO4 = moles
20.9 g of H2O = moles
x =

 

[ThatReallyReallyWeirdDude]

(d) Gypsum is hydrated calcium sulphate, CaSO4.xH2O. It contains 20.9% water by mass.
Calculate x.
Mr: CaSO4, 136; H2O, 18.
79.1 g of CaSO4 = moles
20.9 g of H2O = moles
x =

Alright then
We should find the mole ratio of CaSO4:H2O
so in 79.1g of CaSO4 there is 79.1/ 136=0.58moles
in 20.9g of H2O there is 20.9/18=1.16 moles
so CaSO4:H2O
=0.58:1.16
we want that to be 1:x (since the formula is CaSO4.xH2O, that means there's 1 CaSO4 mole for every x moles of H2O)
so 0.58/0.58:1.16/0.58
=1:2
therefore x=2

 

[JimmyCarter]

Alright then
We should find the mole ratio of CaSO4:H2O
so in 79.1g of CaSO4 there is 79.1/ 136=0.58moles
in 20.9g of H2O there is 20.9/18=1.16 moles
so CaSO4:H2O
=0.58:1.16
we want that to be 1:x (since the formula is CaSO4.xH2O, that means there's 1 CaSO4 mole for every x moles of H2O)
so 0.58/0.58:1.16/0.58
=1:2
therefore x=2

ooookkkk SANK YOU!!

 

[ThatReallyReallyWeirdDude]

ooookkkk SANK YOU!!

You're welcome XD Is it right?
Nevermind, imma sleep now.

 

[JimmyCarter]

You're welcome XD Is it right?
Nevermind, imma sleep now.

yess i checked the markscheme

 

[Dsilentkila]

do all polymerisation reactions require a catalyst ?

 

[chocolate brown ooooh]

I always have problems in mole calculations..,,. Can anyone give me good tips ????

 

[ThatReallyReallyWeirdDude]

I always have problems in mole calculations..,,. Can anyone give me good tips ????

http://www.xtremepapers.com/community/threads/chemistry-paper-3-calculations.16660/#post-289840
Hope that helps.
Also check link to the chemistry notes in my signature, may be useful too

do all polymerisation reactions require a catalyst ?

Bah atm my chemistry notes aren't next to me. I'll get back to you.
Addition Polymerization requires high temperature and catalyst, that's all you need to know.
Condensation...if I remember correctly, it's done in the presence of conc. sulphuricacid

 

[omglaigcse]

how to draw this? W10, qp33
the formula is C4H4O4
Maleic acid is dibasic. One mole of acid produces two moles of H+. Deduce its
structural formula.

 

[ThatReallyReallyWeirdDude]

how to draw this? W10, qp33
the formula is C4H4O4
Maleic acid is dibasic. One mole of acid produces two moles of H+. Deduce its
structural formula.

 

[Dsilentkila]

$alam$ people.
anybody knows which years had the toughest past papers , or a paper which tests u for wide range of topics?
wana test myself

 

[chocolate brown ooooh]

http://www.xtremepapers.com/community/threads/chemistry-paper-3-calculations.16660/#post-289840
Hope that helps.
Also check link to the chemistry notes in my signature, may be useful too

Bah atm my chemistry notes aren't next to me. I'll get back to you.
Addition Polymerization requires high temperature and catalyst, that's all you need to know.
Condensation...if I remember correctly, it's done in the presence of conc. sulphuricacid

thanks a lot!!!!! u made my day!!!

 

[saroooor]

Oh,right. Thnx.

-OOC - C6H4 - COO - CH2 - CH2 -

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