Carbon compounds as fuel and feedstock Flashcards
What is a hydrocarbon?
A molecule made up of only hydrogen and carbon atoms only
What is the general formula for alkanes
alkAne
CnH2n+2
Name the four different alkanes
Methane
Ethane
Propane
Butane
How many carbon atoms in methane?
One
How many carbon atoms in ethane
Two
How many carbon atoms in propane?
Three
How many carbon atoms in butane?
Four
How many covalent bonds do carbon atoms ALWAYS make?
FOUR
Scientists say that alkanes are saturated. What does this mean?
Saturated means that the carbon atoms are fully bonded to the hydrogen atoms with single convalent bonds
What is crude oil
A non-renewable resource
What is crude oil made out of?
Plankton fossilised from millions of years ago
What type of covalent bonds are in alkanes?
Single covalent bonds
How many covalent bonds do hydrogen atoms make in alkanes?
One
Explain the process of fractional distillation
- Crude Oil is heated to a very high temperature. This causes the crude oil to boil and the hydrocarbons evaporate and turn into gas
- This gas is fed into a fractional distillation collumn. The collumn is hotter at the bottom and cooler at the top
- The hydrocarbon vapours rise up the collumn and then condense into a liquid when they reach their boiling point.
Long-chain hydrocarbons have very high boiling points and they condense at the bottom of the collumn. Short-chain hydrocarbons have very low boiling points and they continue to rise, then condense when they reach their boiling points. - The liquid fractions are then removed from the collumn
How are the different fractions separated in fractional distillation
They are separated using their different boiling points
Name two different fuels that are come from crude oil in fractional distillation
Diesel
Petrol
What is diesel used for?
Fuel for lorries
What is petrol used for?
Fuel for cars
What is viscosity?
The thickness of a liquid
What happens to the viscosity of hydrocarbons with increasing molecular size
Viscosity increases
What is flammability?
How easily a hydrocarbon combusts
What happens to the flammability of hydrocarbons with increasing molecular size
Flammability decreases
Do long-chain hydrocarbons have high or low viscosity?
High viscosity
Do short-chain hydrocarbons have high or low viscosity?
Low viscosity
Do long-chain hydrocarbons have high or low to flammabilty
Low flammability
they are hard to combust
Do short-chain hydrocarbons have high or low flammability?
High flammability
they are easy to combust
What happens to the boiling points of hydrocarbons with increasing molecular size
The boiling point increases
Do long-chain hydrocarbons have high or low boiling points?
High boiling points
Do short-chain hydrocarbons have high or low boiling points?
Low boiling points
The combustion of hydrocarbons releases ___
fill in the blank
The combustion of hydrocarbons releases energy
What happens to the carbon and hydrogen in hydrocarbons when they are combusted?
The carbon and oxygen are oxidised
What are the products of the complete combustion of hydrocarbons?
Carbon dioxide + Water
What causes combustion to be complete
When there is an excess of oxygen
What is the complete combustion of hydrocarbons?
When hydrocarbons burn completely in an excess of oxygen to produce carbon dioxide and water
What is incomplete combustion
A combustion reaction in which hydrocarbons are not completely burned as there is not a sufficient supply of oxygen
What are the porducts of incomplete combustion?
carbon (soot) + carbon monoxide + water
What are the tests to find out the presence of water as a product of complete combustion?
Anhydrous copper sulfate changes colour from white to blue when water is present
or
Cobalt chloride paper changes colour from blue to pink when water is present
Why is it dangerous for the incomplete combustion of hydrocarbons to occur in a home setting
Incomplete combustion of hydrocarbons produces carbon monoxide. This is a toxic gas which binds to haemoglobinin blood instead of oxygen
