Concept:When a gas is synthesized in a lab and collected by bubbling it through water, the collected gas is not pure; it mixes with water vapor.
Formula:$$ P_{total} = P_{dry\,gas} + P_{water\,vapor} $$
Solution:- To find the true pressure of the dry gas, we must subtract the "aqueous tension" (partial pressure of the water vapor) from the total measured pressure in the collection flask.
- This principle—that the total pressure is the simple sum of the individual partial pressures of the non-reacting gases in the mixture—is the direct practical application of Dalton's Law of Partial Pressures.
Why other options are incorrect:- Options A & B: Boyle's and Avogadro's laws deal with single-gas volume relationships, not multi-gas mixtures.
- Option D: Graham's law governs the rates of diffusion and effusion, not static partial pressures.
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