CRUDE OIL AND FUELS Flashcards
How is crude oil made?
Remains of tiny, ancient sea animals and plants, mainly plankton, that were buried in mud. Over time, layer upon layer of rock was laid down on top, creating the conditions (high pressure and temperature, in the absence of oxygen) to make crude oil.
What are alkanes?
Most of the hydrocarbons in crude oil are alkanes. Alkanes are saturated hydrocarbons. All the carbon-carbon bonds are single covalent bonds. This means they contain as many hydrogen atoms as possible in each molecule. No more hydrogen atoms can be added.
What is the pattern in the formula of the alkanes?
CnH2n+2
How does fractional distillation work?
Each hydrocarbon fraction contains molecules with similar numbers of carbon atoms. Each of these fractions boils at different temperatures because of their different sizes of molecules in it. Crude oil is hearted and fed in near the bottom of a tall tower (called a fractioning column) as hot vapour. The Colombo is kept hot and the bottom and cooler at the top. The gases move up the column and and the hydrocarbons condense when they reach the temperature of their boiling points. The different fractions are collected as liquids at different levels.
What are the products of complete combustion (of a hydrocarbon)?
Carbon dioxide and water.
How do you test for water?
Using blue cobalt water, it should turn pink if water is present.
What happens when there is not enough air for a substance to burn in?
Incomplete combustion happens.
What are the products of incomplete combustion?
Carbon monoxide gas and/or carbon along with water.
Why use the cracking process?
To break up the heavier fractions that are not high in demand.
How do you test whether a substance is an alkane or an alkene?
A positive test for an unsaturated hydrocarbon is that it turns orange bromine water colourless.
What is crude oil?
Finite resource found in rocks
Formed over millions of years from the remains of Dead Sea animals and plants, mainly plankton
Mixture of many different carbon compounds
Most of the compounds are hydrocarbons (compounds containing carbon and hydrogen only)
Before it can be used, it must be speedster into fractions. This is done by fractional distillation.
How does fractional distillation work?
Crude oil is heated so it turns into a mixture of gases
The gases enter a tall tower called a fractionating column
The column is very hot at the bottom and cooler at the top
Gases move up the column and condense when the temperature matches their boiling point
The different gases have different boiling points, so they condense and are collected at different places on the column.
Fractions with the smallest molecules have the lowest boiling points and are collected at the top of the column.
As you go down the fractionating column what happens to the size of molecules?
Get bigger.
As you go down the fractionating column what happens to the boiling point?
Increases.
As you go down the fractionating column what happens to the volatility?
Decreases (less tendency to turn into a gas)
As you go down the fractionating column what happens to the viscosity?
Increases (get thicker).
As you go down the fractionating column what happens to the flammability?
Get less flammable (harder to set alight).
What are the first four alkanes?
Methane, ethane, propane and butane.
What are the bonds in alkanes?
Covalent.
How many bonds to carbon atoms always have?
Four.
How many bonds do hydrogen atoms always have?
One.
Are alkanes saturated or unsaturated?
Saturated.
What is the general formula for alkanes?
CnH2n+2
What is cracking?
At high temperature, the atoms in an alkane molecule vibrate rapidly. If this temperature is high enough, the vibration becomes sufficiently vigorous for chemical bonds to break. This breakage of the C-C bonds in alkanes leads to the formation of smaller hydrocarbon fragments and is called cracking. The temperature required for cracking can be reduced by using a solid catalyst.
What are alkanes?
Such as ethane are formed during the cracking of alkanes. The contains a carbon carbon double bond. Alkanes are unsaturated. We can test for an alkene using bromine water.
