Comprehensive Study Guide: Hydrocarbons, Crude Oil Refinement, and Environmental Chemistry of Combustion, and Oil Sand Extraction

Definition of Hydrocarbon: A hydrocarbon is a chemical compound consisting entirely and only of the elements hydrogen and carbon.
Alkanes: * Definition: Alkanes are a family of saturated hydrocarbons. This means they contain only single covalent bonds between carbon atoms. * General Formula: The chemical composition follows the formula $C_nH_{2n+2}$ . * Calculation Example: To determine the formula for an alkane with $10$ carbon atoms, apply $n = 10$ to the general formula: $C_{10}H_{(2 \times 10) + 2} = C_{10}H_{22}$ .
Alkenes and Polymers: * Propene: An example of an alkene with the formula $C_3H_6$ . * Chemical Test for Alkenes: To identify an alkene, the substance is treated with bromine water. * Test Result: If an alkene is present, the orange/brown bromine water will decolourise, becoming colourless. * Poly(propene): This substance is a polymer (specifically an addition polymer) produced from propene monomers.

Crude Oil Composition: Crude oil is defined as a complex mixture of various hydrocarbons.
The Fractional Distillation Process (Industrial Separation): * Heating: Crude oil is heated until it evaporates, turning into vapour. * Fractionating Column (Figure 1): The industrial equipment used is a column that maintains a temperature gradient—it is hotter at the bottom and cooler at the top. * Condensation: The hydrocarbon vapours rise through the column. Because different hydrocarbons have different boiling points, they condense (turn back into liquid) at different levels/heights based on the temperature. * Fractions: Hydrocarbons with higher boiling points condense near the bottom, while those with lower boiling points condense higher up.
The Cracking Process: * Definition: Cracking is the chemical reaction where larger alkane molecules are broken down into smaller, more commercially useful molecules. * Balanced Equation Example: The cracking of tetradecane ( $C_{14}H_{30}$ ) into octane ( $C_8H_{18}$ ) and propene ( $C_3H_6$ ) is balanced as: $C_{14}H_{30} \rightarrow C_8H_{18} + 2C_3H_6$ .

Carbon Chain Length: * Petrol molecules range from $4$ to $12$ carbon atoms. * Diesel molecules range from $12$ to $20$ carbon atoms.
Boiling Point Ranges: * Petrol has a lower boiling point range: $40\,^\circ\text{C}$ to $205\,^\circ\text{C}$ . * Diesel has a higher boiling point range: $250\,^\circ\text{C}$ to $350\,^\circ\text{C}$ .

Methane Combustion: * The balanced chemical equation for the combustion of methane fuel is: $CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$ .
Atmospheric Emissions from Engines: * Common exhaust gases include oxides of nitrogen ( $NO_x$ ), carbon monoxide ( $CO$ ), and water vapour ( $H_2O$ ). * Common Element: All three of these common pollutant gases contain the element oxygen.
Specific Pollutant Characteristics: * Oxides of Nitrogen: The nitrogen in these pollutants originates from the air/atmosphere itself, reacting with oxygen at the high temperatures present in a car engine. * Particulates: Burning diesel can produce solid particulates (soot). The environmental effect associated with these is global dimming. * Carbon Monoxide: This gas is particularly dangerous and difficult to detect because it is both colourless and odourless. * Phase of Exhaust Water: Water is released as a vapour (gas) rather than a liquid because the engine's internal temperature is high enough to boil the water produced during combustion. * Sulfur Impurities: Sulfur is frequently found as an impurity in diesel. When burned, it reacts with oxygen to form sulfur dioxide, which leads to the environmental problem of acid rain.

Resource Scale: Canada’s oil sands account for approximately $20\%$ of the world’s known crude oil reserves.
Composition: The sands contain between $10\%$ and $15\%$ crude oil, which exists primarily as bitumen.
Extraction and Mining Procedure: * Deforestation: Large areas of forest are cleared to access the site. * Overburden Removal: Industrial diggers and trucks must remove a depth of $30\,\text{metres}$ of soil and rock. * Quarrying: The exposed oil sands are quarried for processing.
Separation of Bitumen from Sand: * The Boiling Water Method: Quarried sands are mixed with boiling water. This water is heated by burning methane (natural gas). * Buoyancy Separation: The mixture separates naturally because bitumen floats on the water while sand sinks to the bottom.
Downstream Processing: The extracted bitumen must be cracked and then separated via fractional distillation to create petroleum products like petrol.
Environmental and Practical Considerations: * Advantages: Access to massive global reserves ( $20\%$ ); economic fuel production. * Disadvantages: Destruction of forest ecosystems and habitats; massive physical disruption of the earth ( $30\,\text{metres}$ deep); high energy intensive (requires burning methane which releases $CO_2$ ); creates substantial waste sand and requires large volumes of water.