Fuels Practice Questions

State what is meant by the term hydrocarbon.

The table shows the formulae of five substances.

Substance	Formula
ethanol	$\mathrm{C_2H_5OH}$
hexane	$\mathrm{C_6H_{14}}$
chloroethane	$\mathrm{C_2H_5Cl}$
cyclohexane	$\mathrm{C_6H_{12}}$
carbon dioxide	$\mathrm{CO_2}$

Identify the two hydrocarbons in the table.

Apart from their use as fuels, state one other use of the substances obtained from crude oil.

Name the fraction obtained from crude oil that is used to surface roads and roofs.

State a use for each of these two fractions.

gases .....................................................

fuel oil .....................................................

Which fuel is found in natural gas and is not obtained from crude oil?

A petrol

B kerosene

C methane

D diesel oil

Explain why crude oil is described as a finite resource.

Name the two products formed when propane burns completely.

Balance the equation for the complete combustion of propane.

$\mathrm{C_3H_8} + \text{.....}\,\mathrm{O_2} \rightarrow \text{.....}\,\mathrm{CO_2} + \text{.....}\,\mathrm{H_2O}$

State what happens to energy when propane burns in the stove.

Explain how fractional distillation separates crude oil into different fractions.

Molecules in the kerosene fraction contain 11 to 15 carbon atoms. Molecules in the diesel oil fraction contain 16 to 20 carbon atoms.

Explain which of these two fractions is collected higher up the column.

Give the general formula of the alkanes and use it to work out the molecular formula of the alkane with nine carbon atoms.

Hexane is the next member of the series. Predict the boiling point of hexane and explain your prediction using the data in the table.

Apart from having the same general formula, give two other features of a homologous series.

Use the data in the table to explain why some of the fuel oil fraction is cracked at an oil refinery.

Tetradecane, $\mathrm{C_{14}H_{30}}$, can be cracked as shown.

Complete the equation by giving the formula of the single molecule needed to balance it.

$\mathrm{C_{14}H_{30}} \rightarrow \text{.................................} + 2\mathrm{C_3H_6}$

Describe what happens to the hydrocarbon molecules during cracking.

Explain why sulfur dioxide is released from the ship's funnel when this fuel is burned.

Write the balanced equation for the reaction that forms sulfur dioxide.

Explain two problems caused by acid rain that forms from this sulfur dioxide.

Explain how oxides of nitrogen are formed inside the engine.

Give one problem caused by releasing oxides of nitrogen into the air.

Explain why the blocked air vent causes carbon and carbon monoxide to be produced in the boiler.

Give two problems caused by the soot produced inside the boiler.

The engineer tells the owner to fit a carbon monoxide alarm. Explain why carbon monoxide produced by the boiler is dangerous to the people in the house.

Evaluate the use of hydrogen, rather than petrol, as a fuel for cars.

Balance the equation for the complete combustion of octane.

$\text{.....}\,\mathrm{C_8H_{18}} + \text{.....}\,\mathrm{O_2} \rightarrow \text{.....}\,\mathrm{CO_2} + \text{.....}\,\mathrm{H_2O}$

In a poorly maintained engine, octane can burn so that carbon monoxide and water are the only products.

Write the balanced equation for this reaction.

Explain why burning octane in this way releases less energy per gram of fuel than complete combustion.