Read Ideal-Solution Assumptions Before Mixing Volumes
An ideal solution assumes volumes and enthalpies add without any net interaction change on mixing — real deviations from this are exactly what distinguish ideal from non-ideal behaviour.
Chemistry questions first require the material, particles or reaction condition to be identified before a formula or rule is selected.
Volume additivity as the ideal-solution test
For a genuinely ideal solution, the volume of the mixture equals the sum of the component volumes before mixing, and there's no enthalpy change on mixing — any deviation from simple volume addition signals non-ideal (real) solution behaviour.
Converting a mass-based concentration to molarity
Going from a mg-per-kg-of-solvent concentration to molarity needs both the solvent's density (to get total solution volume) and the solute's molar mass — chain unit conversions explicitly rather than trying to shortcut between mass-based and volume-based concentration units.
OlympIQ exam lens
- ✓An ideal solution shows zero volume change and zero enthalpy change on mixing.
- ✓Converting between mass-based and volume-based concentration units always needs density as a bridging step.
- ✓Molarity conversions from a trace concentration (mg/kg) need both density and molar mass applied explicitly.
Don't assume volumes simply add when a real (non-ideal) solution is described — that additivity is specifically the definition of an ideal solution, and many real mixtures show a net volume contraction or expansion.
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