7 1 hydrocarbons fuel and feedstock

Crude oil is made up of a mixture of a large number of compounds including hydrocarbons.

Hydrocarbons are compounds that are made up of carbon and hydrogen only.

False. Crude oil is a finite resource found in rocks.

Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud.

The general formula of an alkane is CnH2n+2.

The name and molecular formula of the alkane containing one carbon atom is methane and CH4.

The name and molecular formula of the alkane containing two carbon atom is ethane and C2H6.

The name and molecular formula of the alkane containing three carbon atom is propane and C3H8.

The fourth alkane is butane, with the molecular formula C4H10.

The name of the following alkane is butane.

The name of the following alkane is ethane.

A displayed formula shows the spatial arrangement of all the atoms and bonds in a molecule.

A general formula tells you the composition of any member of a whole homologous series of organic compound.

Structural formulae show enough information to make the structure clear, but most of the actual covalent bonds are omitted. Only important bonds like double and triple bonds are always shown.

A molecular formula is the actual number of atoms of each element in a compound.

The displayed formula of propane is:

True. Each fraction in crude oil consists of groups of hydrocarbons with similar chain lengths.

Fractional distillation is the process of separating the different fractions of crude oil based on their boiling points.

True. The size and length of each hydrocarbon molecule determines which fraction it will be separated into.

False. As you move up a fractionating column, the temperature decreases.

Liquefied petroleum gas is used for domestic heating & cooking.

True. Kerosene is used as jet fuel (paraffin).

Diesel is used in diesel engines (gas oil).

Heavy fuel oil is used for ships & power stations.

Fractions condense inside the fractionation tower because their vapours rise and reach a point where the temperature is below their boiling point.

Petrol is used as fuels for cars.

False. The vapours of hydrocarbons with high boiling points condense at the bottom of the column.

As the molecules get larger, the intermolecular forces of attraction become greater so more energy is needed to overcome them.

Viscosity is the ease of flow of a liquid.

As the molecular size increases, the viscosity of a hydrocarbon liquid increases.

The products of complete combustion of hydrocarbons are carbon dioxide and water.

The symbol equation for the complete combustion of propane is: C3H8 + 5O2 → 3CO2 + 4H2O

False. Smaller hydrocarbon molecules are more flammable and are easier to ignite than larger molecules

Flammability decreases as alkanes increase in size.

Short chain alkanes better to use as fuels.

Long chain alkanes are useful as lubricants in machinery as they are more viscous.

True. High viscosity liquids are thick and flow less easily.

The purpose of cracking is to convert surplus unwanted fractions of crude oil, such as kerosene and diesel oil, into more useful fractions like petrol (gasoline), alkenes, and hydrogen which are in high demand.

True. The demand for certain fractions outstrips the supply, which is why cracking is necessary to convert surplus unwanted fractions into more useful ones.

The two methods used for cracking alkanes are:

False. Cracking is an endothermic reaction.

The equation for the cracking of decane to produce ethene and an alkane is: C10H22 → C8H18 + C2H4

True. Alkanes are saturated compounds, and alkenes are unsaturated compounds.

The catalyst used in catalytic cracking is:

False: Cracking is a type of thermal decomposition reaction.

True. Long chain fractions are in high supply but in low demand. This explains why they are cracked into more useful, shorter chain alkanes and alkenes.

Uses for the short chain alkenes formed in cracking include:

A long chain hydrocarbon is cracked to form shorter chain alkanes and shorter chain alkenes.

Bromine water is used to test for the presence of a C=C bond.

The colour change when bromine water is added to an alkene is orange to colourless.

True. Alkenes are used to make polymers and are the starting materials for the production of many other chemicals.