C9 - Crude oil and fuels Flashcards
What is meant by the term ‘hydrocarbon’?
A molecule made from Carbon and Hydrogen atoms ONLY
What is the difference between a saturated and an unsaturated hydrocarbon?
A saturated hydrocarbon (eg alkane) does not contain a C=C double bond. An unsaturated hydrocarbon (eg alkene) does contain a C=C double bond and can undergo addition reactions.
What is the name given to molecules which share the same molecular formula but have different structures?
Isomer
Where are alkanes found naturally?
Crude oil or natural gas
Name the first 6 alkanes.
- Methane
- Ethane
- Propane
- Butane
- Pentane
- Hexane
What is the general formula for the alkanes?
CnH(2n+2)
True or false: Butane and methyl propane are isomers?
True
Which substances are made when an alkane burns undergoing complete oxidation?
- Water
- Carbon dioxide
What is meant by the term ‘homologous series’?
A homologous series is a group of organic compounds that have similar chemical properties and have trends in their physical properties (eg boiling points). Each member of the homologous series differs from the previous by a CH2 unit.
Describe what is meant by ‘complete’ and ‘incomplete’ combustion.
- Complete combustion occurs in excess oxygen, producing carbon dioxide
- Incomplete combustion occurs in limited oxygen, producing soot and carbon monoxide
What compound has the formula CO, and why is it dangerous?
Carbon monoxide, poisonous
Which equation represents incomplete combustion?
Equation b) C2H6 + 3.5O2 ——2CO2 + 3H2O
What is the general formula for an alkene?
CnH2n
What is the name of the alkene with 5 carbons?
Pentene
Why is there no such molecule as ‘methene’?
An alkene contains a C=C double bond; the smallest alkene is ethene, not methane.
Why are alkenes more reactive?
Alkenes are unsaturated and contain a C=C double bond that reacts by one of them opening up and reacting.
What is the molecular formula of propene?
C3H6
What colour is bromine water?
Orange
What happens to bromine water if it is added to an alkene?
Changes colour from Orange to colourless
What type of chemical reactions do alkenes undergo?
Addition
Write a chemical equation for the reaction between ethene and bromine water and name the product.
CH2CH2 + Br2 ——CH2BrCH2Br
1,2-dibromoethane
What is crude oil?
A mixture of hydrocarbons
Name the process by which crude oil is separated into its separate components.
Fractional Distillation
Why does fractional distillation work?
The molecules in crude oil have different boiling points and can be separated.
Is the hottest part of the fractionating tower at the top or the bottom?
Bottom
Which fraction has the lowest boiling point?
Refinery gases
Which fraction has the highest boiling point?
Bitumen
True or False: Refinery gases have a high boiling point so they will condense at the top of the tower.
FALSE: Refinery gases have a LOW boiling point so they will condense at the top of the tower.
What happens to the viscosity of the fractions as you move down the fractionating tower?
Viscosity increases
What happens to the boiling points of the fractions as you move up through the fractionating tower?
The boiling points decrease
True or False: When a mixture of hydrocarbons is separated, the bonds within the molecules are broken.
FALSE: The weak bonds between the molecules are broken, NOT the strong covalent bonds between the atoms.
What happens to the flammability of the hydrocarbons as you descend the fractionating tower?
Flammability decreases
Which gas reduces the capacity of the blood to carry oxygen?
Carbon monoxide
Which hydrocarbons are most useful and why?
Smaller ones as more flammable (used as fuels)
When fuels burn in car engines, what unreactive gas in the air burns too?
Nitrogen oxides
What type of pollution does nitrogen oxides cause?
Acid rain
Many fuels contain sulfur. What gas is produced when sulfur burns?
Sulfur dioxide
What type of pollution does sulfur dioxide cause?
Acid rain
Why would a chemist know that carbon dioxide, nitrogen dioxide, and sulfur dioxide are all acidic gases?
They are all non-metal oxides
Give two harmful effects of acid rain.
- Makes lakes and rivers too acidic for aquatic life
- Damages buildings and statues
For which hydrocarbons is there a greater demand?
Smaller chain hydrocarbons
Fractional distillation does not provide enough petroleum to meet the demand. How is this issue resolved?
By Cracking
What are the conditions needed for Cracking?
- High temperature
- Aluminium oxide (alumina) catalyst
Complete the equation: _________——– C2H4 + C6H14.
C8H18
Complete this equation: C15H32 —– C8H18 + C4H8 + ______.
C3H6
True or False: When a long chain alkane is cracked into three smaller short chain molecules, two alkanes and an alkene are produced.
FALSE: There must always be an alkene and an alkane in the products.
How could you prove that at least one of the products of cracking was an alkene?
Use bromine water, it will change colour from orange to colourless.
Why does petrol have a lower boiling point than diesel?
Diesel is made from longer chain hydrocarbons that have stronger attractive forces.
In cracking, how are the physical properties of the smaller chain hydrocarbons different from the larger chain hydrocarbons they were formed from?
- Lower boiling points
- Lower viscosity
- Lower densities
