Question

Which equation is used for atmospheric air-steam mixtures, according to Gibbs Dalton Law?

• A. \( p_B = p_a + p_w \)
• B. \( p_w = p_a + p_B \)
• C. \( p_a = p_w + p_B \)
• D. \( p_T = p_a + p_w \)

Hint:

The Gibbs-Dalton Law is fundamental in thermodynamics and psychrometrics. Remember it as "the total pressure is the sum of the parts" for an ideal gas mixture.

Answer 1

The Correct Option is D

Step 1: State the Gibbs-Dalton Law. The Gibbs-Dalton Law states that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures that each individual gas would exert if it alone occupied the entire volume at the same temperature.
Step 2: Apply the law to the atmospheric air-steam mixture. In this case, the mixture consists of dry air (a) and water vapor or steam (w). The total pressure (\(p_T\)) or barometric pressure (\(p_B\)) is the sum of the partial pressure of the dry air (\(p_a\)) and the partial pressure of the water vapor (\(p_w\)). \[ p_{Total} = p_{air} + p_{water\_vapor} \] \[ p_T = p_a + p_w \] This matches option (4).