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Joined 2026-09-21 Message
Binary mixture 2026-11-05
A binary mixture is a mixture with two specified chemical components. Water mixed with ethanol is a familiar example. “Binary” counts the components used to describe composition, rather than the number of thermodynamic phases: two components can form one homogeneous mixture or coexist in distinct thermodynamic phases.[ref]
1.2 Phases and Classification of Matter. Classification of Matter, homogeneous and heterogeneous mixtures
For two nonreacting components with amounts of substance , the amount fractions satisfyOnly one composition coordinate is independent. In an original preparation using1mole of ethanol and3moles of water, . Using rounded molar masses46.07and18.015grams per mole gives the ethanol mass fractionThus25percent by amount of substance and about46percent by mass describe the same preparation. A composition percentage without its basis is ambiguous. The calculation uses component masses, without assuming additive liquid volume.
Hexane and water illustrate why component count and phase count differ. Their limited mutual solubility permits two liquid thermodynamic phases, each containing some of the other component. A primary compiled experiment equilibrated the liquids by overnight shaking, sampled the aqueous portion with a microsyringe, and measured dissolved hydrocarbon by gas chromatography with flame-ionization detection.[ref]
Hexane with water in the IUPAC-NIST Solubility Database. Record37_269, Experimental Data and Method/Apparatus/Procedure
The liquid immiscibility article develops a lever rule calculation distinguishing each phase's composition from the overall composition.A binary mixture is not automatically an ideal solution. Interactions between unlike molecules can change activities, mixing enthalpy and phase stability. Stating temperature, pressure and the composition basis is therefore part of specifying the system, rather than optional experimental detail.
Mixture Created 2026-10-13 Updated 2026-10-14
A mixture contains two or more chemical substances combined in proportions that need not be fixed. A chemical compound instead has a definite composition: water has two hydrogen chemical atoms per oxygen chemical atom, whereas a sucrose and water mixture can contain different sugar proportions. A homogeneous mixture has uniform composition on the scale of representative samples; a heterogeneous mixture has distinguishable regions of different composition. A chemical solution is homogeneous, whereas sand dispersed in water is a particle suspension.[ref]
1.2 Phases and Classification of Matter. Chemistry 2e, §1.2, Classification of Matter: mixtures, variable composition, homogeneous and heterogeneous examples
The distinction concerns the sample, not merely its ingredient list. A vessel with dissolved sodium chloride and excess undissolved sodium chloride contains a chemical solution and an ionic crystal thermodynamic phase. The liquid portion can be homogeneous while the whole vessel is heterogeneous. Similarly, molecular oxygen dissolved in water is part of a chemical solution; visible gas bubbles introduce a separate gas thermodynamic phase.