Refinery gas, naphtha, kerosene and gas oil are products of the fractionation of crude oil. (a) Explain the underlined term. (b) Name the two major components of liquefied petroleum gas (LPG), a fuel obtained from refinery gas. (i) Why is methanethiol (CH₃SH), a mercaptan, added to natural gas and to LPG? (ii) Calculate the heat of combustion of methanethiol according to the equation: CH₃SH + 3O₂ (g) → CO₂ (g) + 2H₂O (l) + SO₂ (g) The heats of formation of methanethiol, carbon dioxide, water, and sulfur dioxide are –228.3, –393.5, –296.8 and –296.1 kJ mol⁻¹ respectively. (21) (c) Octane is one of the compounds found in naphtha. In an oil refinery it is converted to various other substances by processes A, B and C. Give the IUPAC names for the four hydrocarbon products shown above. (d) Identify the processes B and C. (i) Where are processes A, B and C carried out? (ii) Typically, petrol contains hydrocarbons with 5 to 10 carbon atoms per molecule and diesel contains hydrocarbons with 14 to 19 carbon atoms per molecule. How would you expect the boiling points of petrol and diesel to compare?

Leaving Cert Chemistry Fuel & Thermochemistry: Refinery gas, naphtha, kerosene

Refinery gas, naphtha, kerosene and gas oil are products of the fractionation of crude oil - Leaving Cert Chemistry - Question 6 - 2018

Question 6

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Refinery gas, naphtha, kerosene and gas oil are products of the fractionation of crude oil. (a) Explain the underlined term. (b) Name the two major components of l... show full transcript

Worked Solution & Example Answer:Refinery gas, naphtha, kerosene and gas oil are products of the fractionation of crude oil - Leaving Cert Chemistry - Question 6 - 2018

Step 1

Explain the underlined term.

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Answer

The underlined term refers to the separation or splitting of crude oil into its various components based on differences in molecular size and boiling points. This process is achieved through distillation, where the crude oil is heated, and its components are separated as they vaporize at different temperatures.

Step 2

Name the two major components of liquefied petroleum gas (LPG), a fuel obtained from refinery gas.

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Answer

The two major components of liquefied petroleum gas (LPG) are propane and butane.

Step 3

Why is methanethiol (CH₃SH), a mercaptan, added to natural gas and to LPG?

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Answer

Methanethiol (CH₃SH) is added to natural gas and LPG as an odorant. Since both gases are colorless and odorless, the addition of methanethiol provides a distinct smell, which helps in detecting leaks and ensuring safety.

Step 4

Calculate the heat of combustion of methanethiol according to the equation.

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Answer

To calculate the heat of combustion, we use the heats of formation:

ext{ΔH}_{ ext{combustion}} = ext{Σ ΔH}_{ ext{products}} - ext{Σ ΔH}_{ ext{reactants}}.

Based on the equation:

ext{CH}_3 ext{SH} + 3 ext{O}_2 (g) → ext{CO}_2 (g) + 2 ext{H}_2 ext{O} (l) + ext{SO}_2 (g)

We find:

ext{ΔH}_{ ext{combustion}} = [ ext{ΔH}( ext{CO}_2) + 2 imes ext{ΔH}( ext{H}_2 ext{O}) + ext{ΔH}( ext{SO}_2)] - [ ext{ΔH}( ext{CH}_3 ext{SH}) + 3 imes ext{ΔH}( ext{O}_2)]

Substituting the given values:

Thus,

$ext{ΔH}_{ ext{combustion}} = -1239.1 ext{ kJ mol}^{-1}.$

Step 5

Give the IUPAC names for the four hydrocarbon products shown above.

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Answer

The IUPAC names for the hydrocarbon products are:

2,2,4-trimethylpentane
butane
1-butene
ethylbenzene

Step 6

Identify the processes B and C.

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Answer

Process B is catalytic cracking, and Process C is dehydrocyclization.

Step 7

Where are processes A, B and C carried out?

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Answer

Processes A, B, and C are typically carried out in an oil refinery, specifically in the distillation and conversion units.

Step 8

How would you expect the boiling points of petrol and diesel to compare?

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Answer

Diesel generally has a higher boiling point compared to petrol. This is due to the fact that petrol comprises hydrocarbons with fewer carbon atoms (5 to 10) while diesel has longer-chain hydrocarbons (14 to 19), leading to stronger intermolecular forces and thus higher boiling points for diesel.

Refinery gas, naphtha, kerosene and gas oil are products of the fractionation of crude oil - Leaving Cert Chemistry - Question 6 - 2018

Worked Solution & Example Answer:Refinery gas, naphtha, kerosene and gas oil are products of the fractionation of crude oil - Leaving Cert Chemistry - Question 6 - 2018

Explain the underlined term.

Name the two major components of liquefied petroleum gas (LPG), a fuel obtained from refinery gas.

Why is methanethiol (CH₃SH), a mercaptan, added to natural gas and to LPG?

Calculate the heat of combustion of methanethiol according to the equation.

Give the IUPAC names for the four hydrocarbon products shown above.

Identify the processes B and C.

Where are processes A, B and C carried out?

How would you expect the boiling points of petrol and diesel to compare?

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