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Mole Fraction and Molality

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Mole fraction is a component's moles divided by total moles present; molality is solute moles divided by kilograms of solvent, temperature-independent.

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A solution's molarity shifts slightly as temperature changes its volume, but that same solution's molality stays fixed instead.

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Molality divides by the mass of solvent alone, not the whole solution — confusing the two gives a close but wrong value.