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Ch.6 - Thermochemistry
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoTro 4th EditionCh.6 - ThermochemistryProblema 52
Capitolo 6, Problema 52

The average human lung expands by about 0.50 L during each breath. If this expansion occurs against an external pressure of 1.0 atm, how much work (in J) is done during the expansion?

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First, we need to understand that the work done by a gas during expansion or compression can be calculated using the formula: W = -PΔV. Here, W is the work done, P is the external pressure, and ΔV is the change in volume.
Next, we convert the external pressure from atm to Pa (Pascal) because the SI unit for pressure is Pascal (Pa). We know that 1 atm = 101325 Pa.
Then, we convert the change in volume from liters to cubic meters (m^3) because the SI unit for volume is cubic meters. We know that 1 L = 0.001 m^3.
Now, we substitute the values of P and ΔV into the formula W = -PΔV to calculate the work done during the expansion.
Finally, remember that the work done by the system (in this case, the lungs) on the surroundings is negative, while the work done on the system by the surroundings is positive. So, the work done during the expansion of the lungs will be a negative value.

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Work in Thermodynamics

In thermodynamics, work is defined as the energy transferred when a force is applied over a distance. For gases, work can be calculated using the formula W = PΔV, where W is work, P is pressure, and ΔV is the change in volume. This concept is crucial for understanding how energy is transferred during processes like breathing.
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First Law of Thermodynamics

Pressure-Volume Relationship

The pressure-volume relationship describes how the pressure exerted by a gas changes with its volume. In this context, the external pressure (1.0 atm) acts against the lung's expansion. Understanding this relationship is essential for calculating the work done during the lung's expansion, as it directly influences the amount of energy transferred.
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Relationship of Volume and Moles Example

Units of Work

Work is commonly measured in joules (J) in the International System of Units (SI). One joule is defined as the work done when a force of one newton displaces an object by one meter. In this problem, converting the pressure from atm to pascals and the volume from liters to cubic meters is necessary to ensure that the final work calculation is in joules.
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SI Units
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