4 2 crude oil

Crude oil is a mixture of different hydrocarbons.

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.

As the number of carbon atoms increases, the viscosity of the liquid increases.

As the molecular size increases, the volatility of a hydrocarbon liquid decreases.

Viscosity is the ease of flow of a liquid.

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.

The fraction used for surfacing roads is bitumen.

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

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

Incomplete combustion occurs when there is insufficient oxygen to burn the fuel completely.

The products of incomplete combustion are carbon monoxide, carbon (soot) and water.

Carbon monoxide binds well to haemoglobin, preventing it from binding to oxygen and transporting oxygen to organs.

False. Carbon dioxide is a pollutant causing global warming and climate change.

Incomplete combustion occurs in some appliances such as:

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

The balanced symbol equation for the incomplete combustion of ethane is: C2H6 + 2.5O2 → 2CO + 3H2O

Three gases that the burning of fossil fuels releases:

A fuel is a substance that is burned to release heat / thermal energy

A common impurity in fuels that contributes to acid rain is sulfur. Nitrogen is not accepted.

Nitrogen oxides are formed in the high pressure and temperature conditions of internal combustion engines and blast furnaces.

The equation for the oxidation of sulfur is: S (s) + O2 (g) → SO2 (g)

Acid rain is formed by nitrogen and sulfur oxides dissolve in rainwater to form nitric acid and sulfuric acid, respectively.

Harmful effects of sulfur dioxide include:

Catalytic converters contain transition metal catalysts that convert pollutant gases to less harmful substances through redox reactions.

The equations for the reduction of nitrogen oxides are: 2NO → N2 + O2 2NO2 → N2 + 2O2

Two gases that contribute to acid rain are nitrogen dioxide and sulfur dioxide.

During combustion, the sulfur impurities in the fossil fuels get oxidised / react with oxygen to form sulfur dioxide.

The equation to show the formation of acid rain, H2SO4 (aq), from sulfur dioxide, water and oxygen is: 2SO2 (g) + O2 (g) + 2H2O (l) → 2H2SO4 (aq)

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.

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

False. Cracking is an endothermic reaction.

The equation for the cracking of decane to produce octane and ethene 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.

Examples of longer chain fractions of crude oil are:

Uses for short chain alkenes from cracking include:

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