Dalton's Law of Partial Pressures states that in a mixture of ideal gases, each gas contributes to the total pressure in proportion to its mole fraction, since pressure under the ideal gas law (PV = nRT) depends on the number of particles, not their mass. This belongs to the domain of chemistry/thermodynamics, specifically the kinetic theory of gases and the ideal gas law, and it extends that law from single-component to multi-component gas systems. Because different gas species have different molar masses, mass fraction and mole (particle) fraction diverge, and it is the mole fraction—not the mass fraction—that determines each gas's contribution to total pressure.
Dalton's Law of Partial Pressures states that in a mixture of ideal gases, each gas contributes to the total pressure in proportion to its mole fraction, since pressure under the ideal gas law (PV = …