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#Post#: 13--------------------------------------------------
Chemistry - Group work
DIR By: Dietrech
Date: October 20, 2013, 1:13 pm
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Hydrocarbons - compounds containing atoms of carbon and hydrogen
only.
Saturated hydrocarbons - compounds which have single bonds
between carbon atoms.
Unsaturated hydrocarbons - compounds which have one double bond
between carbon atoms.
Types of hydrocarbons - Alkane, Alkene and Alkyne.
Alkane
1. Prefix (+ane)
2. Meth
3. Eth
4. Prop
5. But
6. Pent
7. Hex
8. Hept
9. Oct
10. Del
Molecular form Structural form
C3H2(3)+2 CH3-CH2-CH3 Propane
C3H8
C4H2(4)+2 CH3-CH2-CH2-CH3 Butane
C4H10
Alkene General formula: CnH2n
C2H2(2) CH2=CH2 Ethene
C2H4
C3H2(3) CH2-CH-CH3 Propene
C4H2(4) CH2-CH-CH2-CH3 Butene
C4H8
C5H2(5) CH2-CH-CH2-CH2-CH3 Pentene
Test to distinguish between alkane and alkene
Reagent: Bromine water
Result with alkane: No reaction takes place, the mixture stays
brown in colour.
Result with alkene: The mixture changes from brown to
colourless.
Combustion: Burning in presence of oxygen.
Complete combustion: Burning in presence of excess oxygen.
CH4+2O2 ---> CO2 + 2H2O
C2H4 ---> 2CO2 + 2H2O
2C2H6 ---> 4CO2 + 6H2O
Incomplete combustion: Burning in limited supply of oxygen.
2CH4 + 3O2 ---> CO + 4H2O
C4H8 + 4O2 ---> 4CO + 4H2O
Cracking
-Breaking of higher hydrocarbons into a mixture of lower alkanes
or alkenes by heating at high temperature in presence of
catalyst is called cracking.
-Hydrogen can also be produced by cracking.
Conditions for cracking
-High temperature
-Catalyst
-Alkene must be smaller than alkane
C9H20 ---> C5H12 + 2C2H4
C10H22 ---> C5H10 + C5H12
C18H[sub]38[/sub] ---> C14H30 + 2C2H4
C8H18 ---> C2H4 + C6H14
Uses of cracking
-Lower hydrocarbons like alkanes are more useful as fuels and
lower alkenes are used as raw materials to make plastics so
cracking is needed to produce lower hydrocarbons which are more
useful.
What is cracking
-Breaking of higher hydrocarbons into a mixture of lower alkanes
and or alkenes by heating at higher temperature in pressure of
catalyst is called cracking.
Why do oil companies crack long chain alkanes?
-Because the longer alkanes (hydrocarbons) can be split into
shorter hydrocarbons which are more useful.
What is formed when a large alkane molecule is cracked?
-Lower hydrocarbons are formed, they can be used as fuels.
Suggest why the demand for petrol and diesel is higher than the
demand for other fractions of crude oil.
-This is because petrol and diesel are used as fuels for all
land vehicles, for example cars and trucks. As we all use
vehicles for transport the consumption of petrol and diesel is
much higher than other fractions of crude oil. This shows us
that demand for petrol and diesel must be higher than demand for
other crude oil fractions like gases, kerosene, fuel oil and
bitumen.
Name the acid present in our stomach
-Hydrochloric acid
Give formula for the following compounds:
Calcium Nitrate
-Ca(NO3)2
Magnesium chloride
-MgCl2
Sodium carbonate
-Na2CO3
Potassium bromide
-KBr
Give the name of the following compounds:
NaCl
-Sodium chloride
Mg(NO3)2
-Magnesium nitrate
K2S
-Potassium sulphide/sulfide
(NH4)2SO4
-Ammonium sulphide/sulfide
What are hydrocarbons? Name any two
-Hydrocarbons are compounds that contain atoms of hydrogen and
carbon only. Examples: Methane, Ethane
Write the word equation for the:
Complete combustion
-Methane + Oxygen ---> Carbon Dioxide + Water
Incomplete combustion
-Methane + Oxygen (limited) ---> Carbon Monoxide +water + soot
-Glass wool is used in experiment to prevent flow of liquid
paraffin, by soaking it up
-Catalyst is used to speed up reaction
-Catalyst should be hot, in between we heat glass wool so liquid
paraffin can vapourise and reach surface of catalyst for
reaction
-Before removing source of heat we should remove delivery tube
to prevent suck back of water which can cause a serious accident
How can you collect various fractions of cracking?
-Fractions are collected by upward delivery tube over water
Write a balanced equation for the cracking reaction (shown in
figure b. [C1.32])
-C10H22 ---> C8H18 + C2H4
You have two liquids, one a fraction of crude oil, the other a
cracked fraction. Explain how you could find out which one is
which.
-In both test tubes, add bromine water and shake it. The one
which will change from brown to colourless contains fractions
obtained from cracking, the other test tube contains the
fraction of crude oil.
(TO BE CONTINUED...)
#Post#: 45--------------------------------------------------
Re: Chemistry - Group work
DIR By: smileonion
Date: May 11, 2015, 11:30 pm
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Because the ship was the knowledge that good.
#Post#: 53--------------------------------------------------
Re: Chemistry - Group work
DIR By: Randomdot
Date: June 2, 2015, 12:22 am
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greatly
#Post#: 69--------------------------------------------------
Re: Chemistry - Group work
DIR By: Loveixus
Date: September 1, 2016, 3:10 am
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#Post#: 109--------------------------------------------------
Re: Chemistry - Group work
DIR By: Numthaneeya
Date: December 13, 2018, 9:48 pm
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#Post#: 150--------------------------------------------------
Re: Chemistry - Group work
DIR By: Davidcop1
Date: October 23, 2019, 5:12 am
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