C7 Hydrocarbons (pg 150) Flashcards
Organic chemistry is about what?
its about compounds that contain carbons. Hydrocarbons are the simplest organic compounds.
Hydrcarbons only contain what atoms?
Hydrogen and carbon Atoms
What is Hydrocarbon?
A hydrocarbon is any compound that is formed from carbon and hydrogen atoms only.
So C10H22 (decane, an alkane) is ahydrocarbon, but CH3COOC3H7 (an ester) is not - it contains oxygen.
What are Alkanes?
they are the simplest type of hydrocarbon you can get. They have the general formular CnH2n+2
The Alkanes are a homologous series, what do this mean?
a group of organic compounds that react in a similar way.
Alkanes are saturated compounds, explain what this means?
each carbon atom forms four single covalent bonds.
What are the first four alkanes?
Methane, Ethane, Propane and Butane
see the displayed formula on page 150, it shows a drawing of all the atoms and bonds in a molecule.
As the length of the carbon chain changes with Hydrocarbons, what happens regarding the properties?
the properties of the hydrocarbon change.
The shorter the carbon chain, what properties of the hydrocarbon change?
the more runny a hydrocarbon is. that is, the less viscous (gloopy) it is.
Hydrocarbons with shorter carbon chains are also more what?
they are more volatile, i.e. they have lower boiling points.
Also the more shorter the carbon chain, the more flammable (easier to ignite) the hydrocarbon is.
The properties of hydrocarbons affect how they’re used for fuels, give some examples:
e.g. short chain hydrocarbons with lower boiling points are used as ‘bottled gasses’ - stored under pressure as liquids in bottles.
When do complete combustion occur?
When there is plenty of Oxygen.
The complete combustion of any hydrocarbon in oxygen releases lots of energy. The only wast products are carbon dioxide and water vapour.
hydrocarbon + oxygen »_space;» carbon dioxide + water (+ energy).
what happens during combustion?
both carbon and hydrogen from the hydrocarbon are oxidised.
What are Hydrocarbons used as, and why?
fuels due to the amount of energy released when they combust completely.
Write a balanced equation for the complete combustion of methane (CH4).
(you need to be able to give a balanced symbol equation for the complete combustion of a simple hydrocarbon fuel when you’re given its molecular formular)
- On the left hand side, ther’s one carbon atom, so only one molecule of CO2 is needed to balance this.
CH4 + ²O2»_space;» CO2 + ²H2O
- On the left hand side, there are four hydrogen atoms, so two water molecules are needed to balance them
CH4 + ²O2 »_space;» CO2 + 2H2O
- There are four oxygen atoms on the right hand side of the equation. Two oxygen molecules are needed on the left to balance them.
CH4 + 2O2 »_space;» CO2 + 2H2O
(please look at diagram on page 180, as symbols are not accurate).
Also see page 99 for more on balancing equations.
