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Author Topic: Chemistry P3 7/6/2010  (Read 24110 times)

Offline soraam

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Re: Chemistry P3 7/6/2010
« Reply #75 on: June 05, 2010, 11:17:45 am »
its easier if you memorized     knaca mgal czn  fe pb  hcu agau                 if youre arab youll see what i mean
and now   my question



how do you know wich is the limiting reagent if the mole ratio is NOT 1:1     :) :)
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Offline Adzel

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Re: Chemistry P3 7/6/2010
« Reply #76 on: June 05, 2010, 11:29:13 am »
Popular Scientists Can Make A Zoo In The Low Humidity Countryside, More Satisfactory...Goodbye

Potassium   K   
Sodium   Na   
Calcium   Ca   
Magnesium   Mg   
Aluminium   Al   
Zinc      Zn   
Iron       Fe
Tin          Sn   
Lead          Pb   
Hydrogen   H   
Copper   Cu   
Mercury
Silver    Ag   
Gold             Au

By the way I forgot who posted this  ???
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Offline Vin

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Re: Chemistry P3 7/6/2010
« Reply #77 on: June 05, 2010, 11:35:41 am »
A@di. ;)
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Offline Dibss

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Re: Chemistry P3 7/6/2010
« Reply #78 on: June 05, 2010, 01:35:55 pm »
Quote from: soraam on June 05, 2010, 11:17:45 am
how do you know wich is the limiting reagent if the mole ratio is NOT 1:1     :) :)
Post a past paper question, it'll be easier to explain =]
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Offline J.Darren

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Re: Chemistry P3 7/6/2010
« Reply #79 on: June 05, 2010, 02:44:27 pm »
Quote from: Adzel on June 05, 2010, 11:29:13 am
Popular Scientists Can Make A Zoo In The Low Humidity Countryside, More Satisfactory...Goodbye

Potassium   K   
Sodium   Na   
Calcium   Ca   
Magnesium   Mg   
Aluminium   Al   
Zinc      Zn   
Iron       Fe
Tin          Sn   
Lead          Pb   
Hydrogen   H   
Copper   Cu   
Mercury
Silver    Ag   
Gold             Au

By the way I forgot who posted this  ???
Mentioning reactivity series we are also required to know that metals above Zinc cannot be extracted by heating with Carbon, metals below Hydrogen does not react with acid to form salt and hydrogen, Copper does not react with steam and cold water, whereas Magnesium, Zinc and Iron only reacts with steam.
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Offline J.Darren

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Re: Chemistry P3 7/6/2010
« Reply #80 on: June 05, 2010, 02:55:14 pm »
Addition polymerisation - Only produces the polymer
Condensation polymerisation - Produces water and polymer

Uses of polymers :

Nylon and terylene - make clothes
Nylon - rope making
PVC - electrical insulator and pipes
Poly(ethene) - bowls, buckes and plastic bags

Plastic and pollution :

- Source of visual pollution
- Burning produces toxic gas

Nylon and proteins :

C=O-OH and NH2 monomers

Proteins has many monomers as it is a biological polyamide, whereas synthetic polyamide, such as nylon, only contains the aforementioned monomers.

When they are joined together, an amide linkage C=O-NH is formed, water is eliminated in forming this linkage.

Amino acids -> Water + Protein (Condensation polymerisation)

Water + Protein -> Amino acids (Hydrolysis, boil with hydrochloric acid)

Polyesters :

C=O-OH and OH monomers

When they are joined together, an ester linkage C=O-O is formed, water is eliminated in forming this linkage.

Fats :

Animal fats and vegetable oils are esters.

Fat (Glyceryl sterate) + Sodium hydroxide -> Sodium salt of long-chain organic acid (Sodium sterate) + Glycerol
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Offline J.Darren

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Re: Chemistry P3 7/6/2010
« Reply #81 on: June 05, 2010, 03:00:36 pm »
Carbonhydrates :

Contains only Carbon, Hydrogen and Water.

The ratio of Hydrogen to Oxygen atoms is in 2:1 ratio.

Glucose - C6H12O6
Starch - (C6H10O5)n

Two OH monomers were joined to form Starch :

-O-[]-O-[]-O-[]-

Glucose -> Starch + Water (Condensation polymerisation)
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Offline J.Darren

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Re: Chemistry P3 7/6/2010
« Reply #82 on: June 05, 2010, 03:12:00 pm »
Acid hydrolysis of complex hydrocarbons :

Heated with dilute HCl, the acid is a catalyst in this reaction.

Starch + Water -> Glucose

The reaction can be catalysed by enzymes, but the sugar produces would be different.

Fermentation :

Glucose -> Ethanol + Carbon Dioxide

Catalysed by enzymes from yeast.

The reaction is an anaerobic respiration of yeast cells, oxygen in air would oxidise ethanol to carbon dioxide.

35 degree celsius - optimal temperature. Too high - enzymens gets denatured. Too low - rate would be too slow to be economical.

Fermentation ceases when the concentration of ethanol reaches 14%, this is because ethanol is poisonous to yeast, and at this concentration yeast dies. All the glucose has been used up.

C6H12O6 -> 2C2H5OH + 2CO2
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Offline Helium

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Re: Chemistry P3 7/6/2010
« Reply #83 on: June 06, 2010, 03:41:59 pm »
Quote from: soraam on June 05, 2010, 11:17:45 am
its easier if you memorized     knaca mgal czn  fe pb  hcu agau                 if youre arab youll see what i mean
and now   my question



how do you know wich is the limiting reagent if the mole ratio is NOT 1:1     :) :)

ya i heard that one before, i heard a chemistry teacher saying,

knaca thin and age of lead...
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Offline sarasa

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Re: Chemistry P3 7/6/2010
« Reply #84 on: June 06, 2010, 03:42:36 pm »
Quote from: J.Darren on June 05, 2010, 03:12:00 pm
Acid hydrolysis of complex hydrocarbons :

Heated with dilute HCl, the acid is a catalyst in this reaction.

Starch + Water -> Glucose

The reaction can be catalysed by enzymes, but the sugar produces would be different.

Fermentation :

Glucose -> Ethanol + Carbon Dioxide

Catalysed by enzymes from yeast.

The reaction is an anaerobic respiration of yeast cells, oxygen in air would oxidise ethanol to carbon dioxide.

35 degree celsius - optimal temperature. Too high - enzymens gets denatured. Too low - rate would be too slow to be economical.

Fermentation ceases when the concentration of ethanol reaches 14%, this is because ethanol is poisonous to yeast, and at this concentration yeast dies. All the glucose has been used up.

C6H12O6 -> 2C2H5OH + 2CO2
Oxygen will oxidise ethanol 2 ethanoic acid, da atmospheric oxygen is not enough to oxidise it to CO2....! da rest r impressive, great work!!!
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Offline princess12

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Re: Chemistry P3 7/6/2010
« Reply #85 on: June 06, 2010, 03:44:30 pm »
GOOD LUCK TO EVERYONE FOR TOMORROW
GOOD LUCK
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Offline 8T

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Re: Chemistry P3 7/6/2010
« Reply #86 on: June 06, 2010, 03:59:03 pm »
Could someone please explain may june 09 paper 32 q 5 b ???
I know it's for instance K3PO4 or T3 PO4.. but the other 2 marks not quite so any help??
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Offline J.Darren

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Re: Chemistry P3 7/6/2010
« Reply #87 on: June 06, 2010, 04:23:57 pm »
Quote from: sarasa on June 06, 2010, 03:42:36 pm
Oxygen will oxidise ethanol 2 ethanoic acid, da atmospheric oxygen is not enough to oxidise it to CO2....! da rest r impressive, great work!!!
Not according to the endorsed revision guide :D
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Offline 8T

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Re: Chemistry P3 7/6/2010
« Reply #88 on: June 06, 2010, 04:34:13 pm »
Could someone please answer me i already feel depressed :S ??
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Offline NidZ- Hero

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Re: Chemistry P3 7/6/2010
« Reply #89 on: June 06, 2010, 05:14:07 pm »
why de rate of rustin is increased in presence of acid and salt water
can sum on eplz answer
thanz in advance  ;D
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