Fractional Distilation of crude oil
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Fractional Distilation of crude oil — Free MYP4 Chemistry Practice Questions

1QuestionCrude oil as a mixture of hydrocarbonsConcept Practice
2 marks~3 minCriterion A
The diagram shows a fractional distillation column used to separate crude oil. Crude oil is fed into the column continuously as a hot vapour–liquid mixture.
a
Identify the substance fed into the bottom of the column. [1]
b
State one property of this substance that makes fractional distillation an effective method of separation. [1]
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2QuestionViscosity and flammability trendsAssessment Practice
4 marks~6 minCriterion C
Three alkane molecules are compared: pentane (C5H12C_5H_{12}), decane (C10H22C_{10}H_{22}), and octadecane (C18H38C_{18}H_{38}).

Observed viscosities: pentane flows like water; decane flows like cooking oil; octadecane flows like honey.

Boiling points: pentane 36°C36°C; decane 174°C174°C; octadecane 317°C317°C.
a
State the trend in viscosity as hydrocarbon chain length increases. [1]
b
Explain how molecular structure influences the strength of London dispersion forces in these three molecules. [1]
c
Using the boiling point data, analyse how the intermolecular force strength accounts for both the boiling point trend and the viscosity trend across these three hydrocarbons. [2]
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Solutions

3QuestionRefinery gasesAssessment Practice
6 marks~9 minCriterion D
Refinery gases — methane (CH4CH_4), ethane (C2H6C_2H_6), propane (C3H8C_3H_8), and butane (C4H10C_4H_{10}) — are burned as fuel in homes and industry. When oxygen supply is limited, incomplete combustion occurs, producing carbon monoxide (COCO) and soot (carbon particles) alongside water, rather than the CO2CO_2 and H2OH_2O predicted by complete combustion. Environmental models of urban air quality frequently assume combustion is 100% complete.
a
Construct balanced chemical equations for both the complete combustion and the incomplete combustion of methane (CH4CH_4), clearly identifying the products in each case. [2]
b
Discuss two health or environmental implications arising specifically from the products of incomplete combustion of refinery gases. [2]
c
Evaluate the limitations of assuming 100% complete combustion when modelling air quality in urban areas. [2]
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Solutions

4QuestionRefinery gasesAssessment Practice
6 marks~9 minCriterion B
Refinery gases from the fractional distillation of crude oil consist of methane (CH4CH_4), ethane (C2H6C_2H_6), propane (C3H8C_3H_8), and butane (C4H10C_4H_{10}).
a
Construct balanced chemical equations, including state symbols, for the complete combustion of each of the four alkanes listed above. [4]
b
Using your equations from part (a), deduce how the molar ratio of CO2CO_2 produced to H2OH_2O produced changes as the number of carbon atoms in the alkane increases. [1]
c
The general formula for alkanes is CnH2n+2C_nH_{2n+2}. Explain, using this formula, why the CO2:H2OCO_2 : H_2O molar ratio approaches but never reaches 1:11:1 as nn increases. [1]

Solutions

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