Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 22 - The Respiratory System - Review Questions - Page 847: 24


According to Dalton's Law of partial pressures, each gas in a mixture of nonreactive gases exerts pressure in proportion to its percentage in the mixture Therefore the total pressure exerted by a mixture of gases is the sum of the partial pressures exerted independently by each gas in the mixture. The total pressure of the major gases in the atmosphere is 760 mm Hg, at seal level The percentages of the major gases in the atmospheric mixture are N2, 78.6%; O2, 20.9%; The rest of the gases in the atmosphere are Argon, Carbon dioxide, (the trace gases) and Hydrogen. According to Dalton's Law Oxygen and Nitrogen accounts for most of the pressure of the atmospheric mixture 756 mm Hg: 78.6\times760 mmHg =597 mm Hg 20.9\times760 mm Hg=159 mm Hg For a total of 756 mm Hg at sea level Henry's Law states that the amount of gas that will dissolve in a liquid is proportional to the partial pressure of the gas in contact with the liquid. Therefore the greater the concentration of gas in the gas phase the larger the amount of the gas that will dissolve in the liquid. The direction of the movement of the gas is determined by its partial pressures in the two phases

Work Step by Step

Nitrogen and Oxygen account for 756 mm Hg of atmospheric pressure at sea level. The balance of 4.0 mm Hg is contributed by Argon, Carbon dioxide, the trace gases, and Hydrogen. By Henry's Law, at equilibrium between gas and liquid phases ,the partial pressures of the gas and liquid are the same. Different gases have different solubilites. Therefore, the unique solubility of the gas, and the temperature must be considered : Carbon dioxide is more soluble than oxygen, but oxygen is more soluble than Nitrogen. Regarding temperature, as liquid temperature rises, gas solubility decreases.
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