Which best defines partial pressure in a mixture of gases
The Correct Answer and Explanation is:
The correct answer is:
Partial pressure is the pressure that a single gas in a mixture would exert if it occupied the entire volume of the mixture by itself at the same temperature.
Explanation
In a mixture of gases, each individual gas contributes to the total pressure in proportion to its amount, which is expressed through the concept of partial pressure. Partial pressure is a fundamental concept in chemistry and physics, especially important in the study of gases and gas laws. The total pressure of a gas mixture is the sum of the partial pressures of all individual gases present, as described by Dalton’s Law of Partial Pressures.
Mathematically, Dalton’s Law is represented as:
[
P_{total} = P_1 + P_2 + P_3 + … + P_n
]
where ( P_1, P_2, P_3, … P_n ) are the partial pressures of the gases in the mixture. Each gas behaves as though it is the only gas present, meaning its partial pressure depends only on the gas’s concentration (moles) and the temperature and volume of the container.
The partial pressure of any specific gas in a mixture can be calculated using the formula:
[
P_{gas} = (X_{gas}) \cdot (P_{total})
]
where ( X_{gas} ) is the mole fraction of the gas, calculated as the number of moles of the gas divided by the total moles of all gases in the mixture.
Partial pressure has practical applications, especially in respiratory physiology and industrial processes. In human lungs, for example, gases like oxygen and carbon dioxide each have their own partial pressures, which drive the processes of gas exchange and diffusion. Oxygen diffuses from areas of higher partial pressure (inhaled air) into blood, where the partial pressure is lower, ensuring that oxygen reaches tissues. Conversely, carbon dioxide moves from blood, where its partial pressure is high, to the lungs for exhalation, where the partial pressure is lower.
Understanding partial pressure helps in predicting how gases will behave in various mixtures and conditions, especially when examining reactions that occur in gaseous states or calculating pressures in closed systems.