The question asks to identify the correct equation representing the Gibbs Dalton Law for atmospheric air-steam mixtures.

Gibbs Dalton Law Explained

Gibbs Dalton Law is a fundamental principle in thermodynamics that describes the behavior of gas mixtures. It states that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas component in the mixture. In simpler terms, each gas contributes its own pressure to the total pressure, independent of the other gases present.

Applying the Law to Air-Steam Mixtures

For an atmospheric air-steam mixture, the total pressure is composed of the pressure exerted by the dry air and the pressure exerted by the water vapor (steam).

• Let $P_B$ represent the total atmospheric pressure of the air-steam mixture.
• Let $P_a$ represent the partial pressure of the dry air component.
• Let $P_w$ represent the partial pressure of the water vapor (steam) component.

According to Gibbs Dalton Law, the sum of the partial pressures of the components equals the total pressure of the mixture. Therefore, the equation is:

This equation indicates that the total pressure ($P_B$) is the sum of the partial pressure of air ($P_a$) and the partial pressure of water vapor ($P_w$). This correctly applies the principle of Gibbs Dalton Law to the specific case of an atmospheric air-steam mixture.

Comparing this to the given options, the equation $P_B = P_a + P_w$ accurately reflects the Gibbs Dalton Law for this context.