Consider the following chemical fuels: H2 CH4 LPG petrol kerosene These fuels burn exothermically in air. (a) Explain the underlined term. (b) Identify a fuel from the list above that (i) is often used in a Bunsen burner, (ii) causes the least environmental impact when burned, (iii) is used in jet aircraft engines and in some central-heating boilers. (c) CH4 is the main component of natural gas. (i) Give the systematic IUPAC name for CH4. (ii) What is the shape of a CH4 molecule? (iii) To which homologous series does CH4 belong? (iv) Why are small quantities of mercaptans added to natural gas before supplying it to consumers? (v) Copy, complete and balance the following equation for the complete combustion of CH4 in oxygen: CH4 + O2 → (d) Propane (C3H8) is one of the two main components of liquid petroleum gas (LPG). (i) Draw the expanded molecular structure of propane, (ii) show the arrangement of all the atoms and bonds in a propane molecule. (iii) Identify the hydrocarbon that is the second main component of LPG.

Leaving Cert Chemistry Fuels & Thermochemistry: Consider the following chemical

Consider the following chemical fuels: H2 CH4 LPG petrol kerosene These fuels burn exothermically in air - Leaving Cert Chemistry - Question 6 - 2020

Question 6

Consider the following chemical fuels: H2 CH4 LPG petrol kerosene These fuels burn exothermically in air. (a) Explain the underlined term. (b) Identify a fuel from... show full transcript

Worked Solution & Example Answer:Consider the following chemical fuels: H2 CH4 LPG petrol kerosene These fuels burn exothermically in air - Leaving Cert Chemistry - Question 6 - 2020

Step 1

Explain the underlined term.

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Answer

The term 'exothermically' refers to the energy lost in a chemical reaction, which is released in the form of heat. In this context, the combustion of the fuels releases energy as it reacts with oxygen, making the enthalpy change (ΔH) negative.

Step 2

Identify a fuel from the list above that (i) is often used in a Bunsen burner.

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Answer

The fuel often used in a Bunsen burner is methane (CH4).

Step 3

Identify a fuel from the list above that (ii) causes the least environmental impact when burned.

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Answer

Hydrogen (H2) causes the least environmental impact when burned, as it produces only water vapor and no carbon emissions.

Step 4

Identify a fuel from the list above that (iii) is used in jet aircraft engines and in some central-heating boilers.

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Answer

Kerosene is used in jet aircraft engines and in some central-heating boilers.

Step 5

Give the systematic IUPAC name for CH4.

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Answer

The systematic IUPAC name for CH4 is methane.

Step 6

What is the shape of a CH4 molecule?

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Answer

The shape of a CH4 molecule is tetrahedral.

Step 7

To which homologous series does CH4 belong?

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Answer

CH4 belongs to the homologous series of alkanes.

Step 8

Why are small quantities of mercaptans added to natural gas before supplying it to consumers?

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Small quantities of mercaptans are added to natural gas to give it a smell, which helps detect leaks and ensures safety.

Step 9

Copy, complete and balance the following equation for the complete combustion of CH4 in oxygen: CH4 + O2 →

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Answer

CH4 + 2 O2 → CO2 + 2 H2O

Step 10

Draw the expanded molecular structure of propane.

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Answer

The expanded molecular structure of propane (C3H8) can be drawn as follows:

       H   H   H
        |   |   |
    H - C - C - C - H
        |   |   |
       H   H   H

Step 11

Show the arrangement of all the atoms and bonds in a propane molecule.

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Answer

In the propane molecule, the arrangement of atoms and bonds includes three carbon atoms connected in a chain, each bonded to enough hydrogen atoms to satisfy carbon's tetravalency, resulting in a structure:

        H   H   H
         |   |   |
     H - C - C - C - H
         |   |   |
        H   H   H

Step 12

Identify the hydrocarbon that is the second main component of LPG.

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Answer

The hydrocarbon that is the second main component of LPG is butane (C4H10).

Consider the following chemical fuels: H2 CH4 LPG petrol kerosene These fuels burn exothermically in air - Leaving Cert Chemistry - Question 6 - 2020

Worked Solution & Example Answer:Consider the following chemical fuels: H2 CH4 LPG petrol kerosene These fuels burn exothermically in air - Leaving Cert Chemistry - Question 6 - 2020

Explain the underlined term.

Identify a fuel from the list above that (i) is often used in a Bunsen burner.

Identify a fuel from the list above that (ii) causes the least environmental impact when burned.

Identify a fuel from the list above that (iii) is used in jet aircraft engines and in some central-heating boilers.

Give the systematic IUPAC name for CH4.

What is the shape of a CH4 molecule?

To which homologous series does CH4 belong?

Why are small quantities of mercaptans added to natural gas before supplying it to consumers?

Copy, complete and balance the following equation for the complete combustion of CH4 in oxygen: CH4 + O2 →

Draw the expanded molecular structure of propane.

Show the arrangement of all the atoms and bonds in a propane molecule.

Identify the hydrocarbon that is the second main component of LPG.

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