GCSE Chemistry Crude oil questions by topic

This question is about hydrocarbons.

1. (a)State what a hydrocarbon is.[1]
2. (b)Give the formula of methane.[1]
3. (c)Explain why C₂H₆ is described as saturated.[1]

Crude oil is separated by fractional distillation.

1. (a)Describe what happens to the crude oil before it enters the column.[2]
2. (b)Explain why the fractions condense at different heights.[2]

Methane burns in air.

1. (a)Complete the word equation for complete combustion: methane + … → … + …[2]
2. (b)Write the balanced symbol equation.[2]

Match each fraction to a use, and state one reason crude oil must be conserved.

1. (a)Petrol[1]
2. (b)Bitumen (residue)[1]
3. (c)State why crude oil is a finite resource.[1]

Complete the table of the first five alkanes.

1. (a)Complete the formula of propane.[1]
2. (b)Complete the formula of butane.[1]
3. (c)Complete the formula of pentane.[1]
4. (d)State the general formula of the alkanes.[1]
5. (e)State what “saturated” means for a hydrocarbon.[1]

This question is about the fractionating column used to separate crude oil.

1. (a)State where in the column the temperature is highest.[1]
2. (b)Name the fraction collected near the bottom of the column and give one use.[2]
3. (c)Explain why short-chain fractions are collected near the top.[2]

The table shows three fractions. Fraction A: 1–4 carbons, gas. Fraction B: 8–12 carbons, runny liquid. Fraction C: over 35 carbons, sticky solid.

1. (a)State the trend in viscosity from A to C.[1]
2. (b)State the trend in boiling point from A to C.[1]
3. (c)State the trend in flammability from A to C.[1]
4. (d)Explain why fraction B (petrol) sells for more than fraction C of the same mass.[2]

This question is about the first four alkanes.

1. (a)Write the general formula of the alkanes.[1]
2. (b)Give the names and formulae of the first four alkanes.[3]
3. (c)Explain the meaning of saturated.[2]

A boiler burning methane develops a fault and receives too little air.

1. (a)Name two products of incomplete combustion.[2]
2. (b)Explain why one of them is dangerous to the household.[2]
3. (c)State what would be observed about the flame, and what it indicates.[2]

Octane (C₈H₁₈) can be cracked.

1. (a)Define cracking.[1]
2. (b)State the conditions used.[2]
3. (c)Octane cracks to give ethene (C₂H₄) and one other product. Give the name and formula of that product.[2]

Write balanced equations for the complete combustion of two gaseous alkanes.

1. (a)Propane, C₃H₈, burning in plenty of oxygen.[2]
2. (b)Pentane, C₅H₁₂, burning in plenty of oxygen.[2]
3. (c)State two effects of releasing the products of complete combustion into the atmosphere in large quantities.[2]

A catalytic cracker processes long alkane molecules from a surplus fraction.

1. (a)Write an equation for octane, C₈H₁₈, cracking into hexane and one other product.[2]
2. (b)Explain why the second product must be an alkene.[2]
3. (c)Predict the products when dodecane, C₁₂H₂₆, cracks to release ethene.[2]

Decane (C₁₀H₂₂) is cracked over a hot catalyst.

1. (a)Write the balanced equation for decane cracking to give ethene and octane.[2]
2. (b)Explain how you know the equation is balanced.[2]
3. (c)Explain why cracking is carried out on a large scale even though distillation already separated the oil.[3]

A student adds orange bromine water to two unlabeled liquids, X and Y. With X the bromine water goes colourless immediately; with Y it stays orange.

1. (a)Identify which liquid is unsaturated and name its bond type.[2]
2. (b)Explain why the colour change happens with that liquid.[2]
3. (c)Write the equation for bromine water’s bromine (Br₂) reacting with ethene.[2]

Compare the combustion of ethene, C₂H₄, in plenty and in too little oxygen.

1. (a)State the products of complete combustion.[2]
2. (b)Explain how a burner flame reveals whether combustion is complete.[2]
3. (c)Write the balanced equation for the complete combustion of ethene.[3]

A refinery holds a surplus of tetradecane (C₁₄H₃₀).

1. (a)State why crude oil fractions like this are a finite resource.[1]
2. (b)Explain why the refinery would choose to crack this fraction.[3]
3. (c)Complete the equation: C₁₄H₃₀ → C₅H₁₂ + C₂H₄ + ?[3]
4. (d)State one use for the alkene produced.[1]

This question is about the pollutants released when fossil fuels burn.

1. (a)State how carbon monoxide forms.[1]
2. (b)State one effect of carbon monoxide.[1]
3. (c)State how sulfur dioxide forms.[1]
4. (d)State how particulates form.[1]
5. (e)State one effect of particulates.[1]
6. (f)Explain why carbon dioxide is not classed as a pollutant that harms the person breathing it directly, yet still concerns scientists.[2]

A refinery has a large surplus of tetradecane, C₁₄H₃₀, whose fraction sells poorly, while demand for short-chain products is strong.

1. (a)Write an equation for cracking tetradecane into ethene plus one other hydrocarbon.[2]
2. (b)Name the other product and state its family.[1]
3. (c)Explain why the refinery carries out cracking rather than simply storing or dumping the surplus.[2]
4. (d)Give two reasons the demand for short-chain hydrocarbons outstrips the fraction supplied naturally by crude oil.[2]
5. (e)State one condition needed for this cracking process.[1]