Qualification > Sciences
IGCSE CHEMISTRY DOUBTS
gaurav95:
One more q
do we have cyclic hydrocarbons i guess one q had come abt properties
can somebody give info abt topics related to this..........
anonymous7:
--- Quote from: Ivo on June 03, 2010, 02:40:53 pm ---OK, We know from the graph that 12cm3 of aqueous sodium hydroxide was needed to react with 4cm3 of aqueous iron(III) chloride. Because they were all at 1.0 mol/dm3, we therefore realise that 1 mole of aqueous iron (III) chloride reacted with 3 moles of aqueous sodium hydroxide. Therefore, the formula for the precipitate is Fe(OH)3.
For iron (II) chloride, we know the formula of the precipitate to be Fe(OH)2, and so for the same volume of aqueous iron (II) chloride - 4cm3, we know 8cm3 of sodium hydroxide was required. Therefore, you would need to draw the maximum height of the precipitate when volume has reached 8cm3.
Hope this has helped! ;D
--- End quote ---
Ohmigod. I actually feel stupid now. Hahah. Thanks. That really did it. ^.^
JD46:
HEy guys ,i'm really in trouble, the problem is that my chemistry guide(bob berry) is missing an important page(Pg 33 to 34) ,about excess reagents and coincidentally ,i always mess up that question and lose marks,so could someone scan the page off the guide and post it,or even a picture would do, i'm sure you''ll wil understand ,thanks! :D ;) :) :)
Ivo:
--- Quote from: gaurav95 on June 04, 2010, 04:46:40 am ---but there are OH groups also so i thought that it could be alcohol but its not like that right ???????????????
and also same q paper q 7 biii.......................pls
--- End quote ---
You would not need to incorporate and OH groups, because they only ask for molecular formula. If they ask for the structual formula, then yes, but that would be complicated.
I'll give you an example:
Butane: Molecular formula - C4H10; Structual formula - CH3CH2CH2CH3.
Vin:
--- Quote from: gaurav95 on June 04, 2010, 04:46:40 am ---but there are OH groups also so i thought that it could be alcohol but its not like that right ???????????????
and also same q paper q 7 biii.......................pls
--- End quote ---
Depends on the q, here its vitamin C. Usually all vitamins contain -OH groups. Only for the structural formula you need to specify -OH and not the molecular formula. ;)
For Q.7 b)iii) There are 'n' number of types of chlorination. This depends on how much chlorine you use and which hydrocarbon you use.
When chlorination occurs it replaces one hydrogen atom from the hydrocarbon and forms HCl
E.g. Chlorination of methane::
H H
| |
H- C - H + Cl2 ------> H- C - Cl + HCl
| |
H H
CH4 + Cl2 ----> CH3Cl + HCl
Product:: Chloromethane (methyl chloride)
Similarly,
CH3Cl + Cl2 ----> CH2Cl2 + HCl
Product:: Dichloro methane (methylene chloride)
CH2Cl2 + Cl2 ----> CHCl3 + HCl
Product:: Trichloro methane (Chloroform)
CH3Cl3 + Cl2 ----> CCl4 + HCl
Product:: Tetrachloro methane (Carbon tetrachloride/Pylene)
I think you only need to know the names in bold. For your question, choose any of the following reaction BUT using butane and chlorine
Eg. C4H11Cl + Cl2 ----> C4H10Cl + HCl
OR to be safe give acc. to the ques
CH3-CH2-CH2-CH2-Cl + Cl2 ----> CH3-CH2-CH2-CHCL2 + HCl
H H H H H H H Cl
| | | | | | | |
H-C-C-C-C-Cl + Cl-Cl----> H-C- C-C-C-Cl + H-Cl
| | | | | | | |
H H H H H H H H
Don't understand anything.. pls. ask.. Just under the concept of chlorination ;) they may ask any other alkane next time
Draw the structures yourself you'll understand better
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version