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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 14th Edition
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Capitolo 5, Problema 80c

Methanol (CH3OH) is used as a fuel in race cars. (c) Calculate the heat produced by combustion per liter of methanol. Methanol has a density of 0.791 g/mL.

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Determine the balanced chemical equation for the combustion of methanol: \( 2 \text{CH}_3\text{OH} + 3 \text{O}_2 \rightarrow 2 \text{CO}_2 + 4 \text{H}_2\text{O} \).
Find the molar mass of methanol (CH3OH) by adding the atomic masses of its constituent atoms: C, H, and O.
Calculate the number of moles of methanol in 1 liter using its density: \( \text{Density} = 0.791 \text{ g/mL} \), so \( 1 \text{ L} = 1000 \text{ mL} \).
Use the enthalpy change of combustion for methanol (usually given or found in tables) to find the total heat produced by the moles of methanol calculated in the previous step.
Convert the heat produced from moles to per liter by using the relationship between moles and volume derived from the density.

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Combustion Reaction

A combustion reaction is a chemical process in which a substance (usually a hydrocarbon) reacts with oxygen to produce heat, light, carbon dioxide, and water. In the case of methanol (CH3OH), the combustion reaction can be represented as CH3OH + 1.5 O2 → CO2 + 2 H2O, releasing energy. Understanding this reaction is crucial for calculating the heat produced during combustion.
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02:24
Combustion Apparatus

Heat of Combustion

The heat of combustion is the amount of energy released when a specific amount of fuel is burned completely in oxygen. It is typically expressed in kilojoules per mole (kJ/mol). For methanol, this value can be found in tables of thermodynamic data, and it is essential for determining the total heat produced per liter of methanol during combustion.
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Percorso guidato
02:24
Combustion Apparatus

Density and Volume Conversion

Density is defined as mass per unit volume and is crucial for converting between the mass of a substance and its volume. In this case, the density of methanol (0.791 g/mL) allows us to calculate the mass of methanol in a given volume (e.g., 1 liter). This conversion is necessary to relate the volume of methanol used to the heat produced during its combustion.
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Density Conversion Example
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