State the reaction type that hydrocarbons undergo when they are used as fuels.
Write the equation for octane, $\text{C}_8\text{H}_{18}$, reacting as a fuel, as in (a)(i).
The amount of material obtained straight from crude oil and suitable for use as fuels is not enough to satisfy demand. One process is used to turn some of the larger hydrocarbon molecules into more useful substances. Name this process.
Besides fuels, this process also makes compounds that can be used to produce polymers. One example is but-2-ene, $\text{CH}_3\text{CH}=\text{CHCH}_3$. Draw the repeat unit of the polymer made from but-2-ene.
Name the type of polymerisation that takes place during the production of the polymer in (b)(ii).
Gases formed in internal combustion engines include carbon monoxide, oxides of nitrogen such as $\text{NO}_2$, and unburnt hydrocarbons. These gases are taken out of the exhaust before they can be released into the atmosphere. State what is used to remove these gases from the exhaust.
Write one equation to show how carbon monoxide, $\text{CO}$, and nitrogen dioxide, $\text{NO}_2$, are removed from the exhaust.
State the environmental effect of allowing unburnt hydrocarbons to enter the atmosphere.
Vehicle fuels are desulfurised. If sulfur is present in a fuel when it burns, $\text{SO}_2$ is produced and may enter the atmosphere, where it can form acid rain. Acid rain can contribute to breathing difficulties. Identify two other consequences of acid rain in the atmosphere.
$\text{NO}_2$ takes part in the formation of acid rain from $\text{SO}_2$. Give two equations that describe how acid rain is formed by the action of $\text{NO}_2$ with $\text{SO}_2$.
$\text{NO}_2$ is called a catalyst in this process. Explain, with the help of a suitable equation, why $\text{NO}_2$ is described as a catalyst.