Topic 8 - Chemical Analysis

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What is a hydrocarbon?
A hydrocarbon is any molecule that contaisn only carbon and hydrogen atoms
What is an alkane?
An alkane is a hydrocarbon. It consits of a chain of carbon atoms surrounded by hydrogen and has the general formula of Cn H2n+2 where n is the number of carbon atoms
What is the formula for Methane
CH4
What is teh formula for ethane
C2H6
What is the formula for propane
C3H8
What is the formula for butane?
C4H10
Why is an alkane saturated?
Because all of its atoms are bonded to as many other atoms as they can
How many bonds can carbon form?
4
How many bonds can hydrogen form?
1
What are the three trends in the properties of hydrocarbons?
The shorter the molecuse the less viscous it is (it is more runny)The shorter the molecule the lower the boiling point isThe shorter the molecule, the more flammable the hydrocarbon is
What is the general equation for the combustion of a hydrocarbon?
hydrocarbon + oxygen → carbon dioxide + water vapour
What is crude oil?
Crude oil is a mixture of many compounds, most of which are hydrocarbons. Most of the hydrocarbons in crude oil are alkanes
How is crude oil formed?
Crude oil is mainly formed from the remains of plankton, plants and animals that are compressed at high temperatures and pressures for millions of years
How is crude oil seperated into different hydrocarbons?
By fractional distillation
How does fractional distillation seperate crude oil?
The crude oil is first turned into a gas and is then pumped into the bottom of a fractionating columnThe different hydrocarbons have different boiling points so condense and lave the fractionating collumn t different points up itShorter chains leave the collumn higher up as they have a lower boilin point
What are the uses of the hydrocarbons that leave the fractionating collumn and when do they leave?
What are the six uses for fractions and where do they exit the collumn?
How does the petrochemical industry use hydrocarbons?
They use some hydrocarbons as feedstock to make new compounds to be used in making useful things
Give 4 things the petrochemical industry uses hydrocarbons to make
lubricantssolventspolymersdetergents
What is a homologous series?
A homologous series is series of compounds which: have the same general formula and have similar chemical properties
What is an organic compound?
A compound that contains carbon atoms
What is cracking?
Cracking is a process used to convert long chain hydrocarbons into shorter, more useful chains
Why are short chain hydrocarbons more useful than longer ones?
They are flammable so make better fuels
What ar ethe two methods of cracking?
Catalyctic cracking steam cracking
How does catalyctic cracking work?
The long chai hydrocarbons are heated so they become a gasThe vapour is passed over a hot catalyst which splits the hydrocarbons apart
How does steam cracking work?
The long chain hydrocarbons are heated so they become a gasThe vapour is mixed with steam and heated to a very high temperature which splits the hydrocarbons
What type of reaciton is cracking?
thermal decomposition
An alkene is an unsaturated hydrocarbon.There are more reactive than alkanes. They have a double covalent bond between two of the carbon atoms in their chain
Why are alkenes unsaturated?
they contain 2 fewer hydrogen atoms than an alkane of the same number of carbon atoms
What is the general formula for an alkene?
CnH2n
What si the formula for ethene
C2H4
What is the formula for propene
C3H6
What is the formula for butene
C4H8
What is the formula for pentene
C5H10
How can you test for alkenes?
Add bromine water to an alkene and it will become colourless. Adding it to an alkane it would remian ornage
What is the general equation for the incomplete combustion of alkenes?
alkene + oxygen →carbon (soot)+carbon monoxide + water + carbon dioxide
What type of combustion do alkenes undergo in air and why?
Incomplete combustion. There is not enough oxygen present in the air
What happens during an incomplete combustion reaction of an alkene?
A smoky yellow flame and less energy being released
How do alkenes burn in air
With a smoky yellow flame. They undergo incomplete combustion as there is not enough oxygen in the air
What is a functional group
A group of atoms in the compiund that determine how the compound typically reacts