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Qualification => IGCSE/ GCSE => Reference Material => Topic started by: Got Tech? GO TECH on June 03, 2010, 09:15:17 am

Title: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Got Tech? GO TECH on June 03, 2010, 09:15:17 am
Reactions and the Catalysts needed for such reactions as well as the conditions in terms of pressure and temperature

Cracking:
Alkane +heat= alkene +alkane OR alkene +alkane +hydrogen
Conditions for Reaction: Aluminum oxide and chromium oxide 500 Centigrade

Addition reaction of ethene and steam to form ethanol:
X-ene + steam= X-anol
Conditions for reaction: Phosphoric acid catalyst, 300centigrade 60 ATM

Obtaining Hydrogen from methane for use in Haber’s process:
Methane + steam= hydrogen+ carbon monoxide
Carbon monoxide + steam= hydrogen + carbon dioxide
Left over steam is reduced by the reducing agent carbon monoxide
Conditions for reaction: nickel catalyst, 750 centigrade, 30 ATM

Haber’s Process:
Nitrogen + hydrogen (ratio 1:3)= ammonia
Conditions for reaction: Finely divided iron catalyst 450 centigrade 200 ATM

Contact Process (formation of Sulfur trioxide):
Sulfur dioxide + oxygen= sulfur trioxide
Conditions for reaction: vanadium pent oxide catalyst, 450 centigrade

Oxidation of Ethanol to form Ethanoic acid:
Ethanol + oxygen = ethanoic acid + water
Conditions for reaction: It’s not exactly a catalyst but the reaction needs an oxidizing agent for ethanol to oxidize.  Heated Potassium dichromate can be used as it is an oxidizing agent, and during the reaction the potassium dichromate turns from orange to green.

Esterification:
X-oic acid + Y-anol = Y-yl X-anoate
EG: Butanoic acid + heptanol= heptyl butanoate
Conditions for reaction: A few drops of concentrated Sulfuric acid as a catalst

Halogenation (formation of chloroethane, dichloroethane..etc)
Alkane + Chlorine radicals = chloroalkane + hydrogen chloride(HCl)
Conditions for reaction: To obtain chlorine radicals lead tetra-ethyl can be used, or UV rays are used.

That’s all I’ve got for now. If you have any similar additions it would be much appreciated.  

NOTE: Previously for the production of Alcohol, I stated that ethane is reacted with steam, I noticed my mistake, and it's supposed to be ethene. PLEASE take a not of this modification!
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: $H00t!N& $t@r on June 03, 2010, 02:32:38 pm
hey Thanks ALOT!!!! its really helpful
+rep !! keep it up  ;)
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: username on June 03, 2010, 03:17:27 pm

thx ismail
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: holtadit on June 03, 2010, 03:28:50 pm
@Got Tech? GO TECH    Potassium Dichromate changes from ORANGE to green not yellow.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: J.Darren on June 03, 2010, 03:54:01 pm

Contact Process (formation of Sulfur trioxide):
Sulfur dioxide + oxygen= sulfur trioxide
Conditions for reaction: vanadium pent oxide catalyst, 450 centigrade

- @ Atmospheric pressure
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Got Tech? GO TECH on June 03, 2010, 04:35:51 pm
@Got Tech? GO TECH    Potassium Dichromate changes from ORANGE to green not yellow.

sorry, thanks for the correction!
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Got Tech? GO TECH on June 03, 2010, 04:37:50 pm
Contact Process (formation of Sulfur trioxide):
Sulfur dioxide + oxygen= sulfur trioxide
Conditions for reaction: vanadium pent oxide catalyst, 450 centigrade

- @ Atmospheric pressure

 i dont have any references to the atm needed for the reaction. do you have any suggestions?
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: elemis on June 03, 2010, 04:40:57 pm
i dont have any references to the atm needed for the reaction. do you have any suggestions?

Its one atmosphere pressure.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Got Tech? GO TECH on June 03, 2010, 04:43:36 pm
Its one atmosphere pressure.

thats what i thought, if there no references to it then it would probably be carried out at atm.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: elemis on June 03, 2010, 04:46:09 pm
thats what i thought, if there no references to it then it would probably be carried out at atm.

No, one of the requirements IS one atm. If your write that in the exam you get one mark.

Obviously one atm is 100KPa  which is the atm pressure under normal conditions.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Got Tech? GO TECH on June 03, 2010, 04:48:20 pm
No, one of the requirements IS one atm. If your write that in the exam you get one mark.

Obviously one atm is 100KPa  which is the atm pressure under normal conditions.

but wouldnt it be 1 atm by default, since the atmosphere always has a pressure of 1 bar?
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Ivo on June 03, 2010, 04:50:09 pm
but wouldnt it be 1 atm by default, since the atmosphere always has a pressure of 1 bar?

As long as you say it is carried out at atmospheric pressure and at 450OC you'll get the marks.  And a vanadium(V) oxide catalyst.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: elemis on June 03, 2010, 04:51:19 pm
but wouldnt it be 1 atm by default, since the atmosphere always has a pressure of 1 bar?

True, but for some reason you get awarded a mark for saying that when asked for the requirements.

However, I must agree it is a flimsy point and I would suggest you DONT use it.

The catalyst and temp are better ones. ;)
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Baladya on June 03, 2010, 05:00:05 pm
yooo help appreciated man :D
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Got Tech? GO TECH on June 03, 2010, 05:00:28 pm
True, but for some reason you get awarded a mark for saying that when asked for the requirements.

However, I must agree it is a flimsy point and I would suggest you DONT use it.

The catalyst and temp are better ones. ;)

Yeah they won't ask for more than 2 reqs..thanks!
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Got Tech? GO TECH on June 03, 2010, 05:51:10 pm
yooo help appreciated man :D

No problem!
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: J.Darren on June 03, 2010, 08:08:07 pm
In oxidation of alcohol to alkanoic acid, the potassium dichromate oxidising agent needs to be ... heated or hot.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Ivo on June 03, 2010, 08:13:27 pm
In oxidation of alcohol to alkanoic acid, the potassium dichromate oxidising agent needs to be ... heated or hot.

When making ethanoic acid from ethanol, you heat the mixture of ethanol, potassium manganate(VII) and sulphuric acid.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Got Tech? GO TECH on June 03, 2010, 08:31:39 pm
In oxidation of alcohol to alkanoic acid, the potassium dichromate oxidising agent needs to be ... heated or hot.

Yeah forgot about that, sorry I left it out, I'll edit it at once.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: Got Tech? GO TECH on June 04, 2010, 07:51:47 am
In fact, you need 2 ATM for sulphur dioxide--> sulphur trioxide...just saw it in w09 q6. they state that you need 450 C and 2 Atmospheres pressure.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: elemis on June 04, 2010, 07:57:21 am
In fact, you need 2 ATM for sulphur dioxide--> sulphur trioxide...just saw it in w09 q6. they state that you need 450 C and 2 Atmospheres pressure.

1-2 atm is fine.
Title: Re: CHEMISTRY GUIDE-A guide to special conditions needed for various reactions
Post by: J.Darren on June 04, 2010, 12:00:24 pm
Fermentation :

Glucose -> Ethanol + Carbon dioxide

Catalyst - Enzymes from yeast.
35 centigrade - if too low the rate would be too slow, if too high the enzymes will be denatured.
When concentration of ethanol reaches about 14%, fermentation ceases becuase all the glucose has been used up / yeast dies at this concentration - ethanol is poisonous to yeast.
Carried out in absence of air as fermentation is an anaerobic respiration of yeast cells.

Acid hydrolysis of complex hydrocarbons :

Heated with dilute hydrochloric acid.
The acid is the catalyst.

Starch + water -> Glucose

Hydrolysis of proteins :

Protein + water -> Amino acids

Boiled with hydrochloric acid.