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Module 8 in the Syllabus

Solution Chemistry Practice Items
Problem set for Solution Chemistry in PDF format

Answer Key
Answers and explanations

Solutions Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Solutions
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Overview of Solutions
A solution is a homogeneous mixture of two or more substances, distinguished from non-homogeneous mixtures such as colloids and suspensions. There may be solid, liquid, or gaseous solutions. For certain types of liquid solutions, it is useful to describe the solution as comprised of one or more solutes dissolved within a solvent. The solubility of a solute describes its ability to dissolve in a certain solvent. A variety of concentration expressions are useful within different contexts to describe the composition of a solution including mole fraction, percent by weight, molarity, and molality. The colligative properties refer to the changes that occur in the physical properties of a solvent when a solute is added to it such as boiling point elevation, freezing point depression, and vapor pressure lowering.

For certain types of aqueous solutions of sparingly soluble electrolytes, an equilibrium will be established at low concentration between the dissolved ions and undissolved solute or precipitate which can be quantatively described using the solubility product corresponding to particular ion pairs.

Solutions on the MCAT
If you do not know this material backwards and fowards, you will suffer on the MCAT. The topic of Solutions is one of the most important for the MCAT. Nearly every exam will require you predict solubility. You can also expect to apply what you understand about the colligative properties and puzzle through something involving heterogeneous solution equilibria. Do not neglect this material. Solutions will be on the test in a direct way.

Conceptual Vocabulary
MixtureIn chemistry, a mixture is a substance made by combining two or more different materials in such a way that no chemical reaction occurs.
SolutionA solution is a homogeneous mixture composed of two or more substances.
PrecipitationPrecipitation is the formation of a solid in a solution during a chemical reaction.
ConcentrationConcentration is the measure of how much of a given substance there is mixed with another substance.
SolubilitySolubility is a physical property referring to the ability for a given substance, the solute, to dissolve in a solvent.
Aqueous solutionA aqueous solution is a solution in which the solvent is water.
CrystallizationCrystallization is the natural or artificial process of formation of solid crystals from a uniform solution.
Boiling-point elevationBoiling-point elevation is a colligative property that states that a solution will have a higher boiling point than that of a pure solvent after the addition of a dissolved solute.
SolvationSolvation or dissolution is the process of attraction and association of molecules of a solvent with molecules or ions of a solute.
Solubility equilibriumSolubility equilibrium is any chemical equilibrium between solid and dissolved states of a compound at saturation.
Colligative propertiesColligative properties are properties of solutions that depend on the number of particles in a given volume of solvent and not on the mass of the particles.
Freezing-point depressionFreezing-point depression is the difference between the freezing points of a pure solvent and a solution mixed with a solute.
Molar solutionA molar solution is one that contains one mole of solute per liter.
Common-ion effectThe common-ion effect is a term used to describe the effect on a solution of two dissolved solutes that contain the same ion.
Dalton's lawDalton's law states that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture.
CarbonationCarbonation occurs when carbon dioxide is dissolved in water or an aqueous solution.
Carbonated waterCarbonated water is plain water into which carbon dioxide gas has been dissolved.
DissociationDissociation is a general process in which ionic compounds separate or split into smaller molecules, ions, or radicals, usually in a reversible manner.
Mole fractionThe mole fraction of a component in a mixture is the relative proportion of molecules belonging to the component to those in the mixture, by number of molecules.
ElectrolyteAn electrolyte is a substance containing free ions that behaves as an electrically conductive medium.
Raoult's lawRaoult's law states that the vapor pressure of an ideal solution is dependent on the vapor pressure of each chemical component and the mole fraction of the component present in the solution.
Henry's lawHenry's law states that at a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
ColloidA colloid, emulsion or dispersion is a type of heterogeneous mixture consisting of a dispersed phase made of tiny particles or droplets distributed evenly throughout a continuous phase.
SupersaturationThe term supersaturation refers to a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances.
Percentage solutionPercentage solution is a form of concentration expression often preferred to molarity within the biological sciences in which a 1 percent solution would have 1 g of solute dissolved in a final volume of 100 ml of solution.
EmulsionAn emulsion, dispersion or colloid is a mixture of two immiscible substances in which a dispersed phase made of tiny particles or droplets is distributed evenly throughout a continuous phase.
Solvation shellSolvation shell is a shell of any chemical species acting as a solvent, surrounding a solute species.
SuspensionA suspension is a heterogenous fluid containing solid particles that are sufficiently large for sedimentation.
Partition coefficientA partition or distribution coefficient is the ratio of concentrations of a compound in the two phases of a mixture of two immiscible solvents at equilibrium.
Van't Hoff factorThe van't Hoff factor is the number of moles of solute actually in solution per mole of solid solute added.
Enthalpy change of solutionThe enthalpy change of solution is the enthalpy change when one mole of a substance is dissolved completely in a large volume of a solvent at constant pressure.
AlloyAn alloy is a homogeneous hybrid of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties.
AzeotropeAn azeotrope is a mixture of two or more pure compounds in such a ratio that its composition cannot be changed by simple distillation.
Multiphasic liquidA multiphasic liquid is a mixture consisting of more than two immiscible liquid phases.
Ideal solutionAn ideal solution or ideal mixture is a solution in which the enthalpy of solution is zero.
Advanced terms that may appear in context in MCAT passages
SurfactantSurfactants, also known as tensides, are wetting agents that lower the surface tension of a liquid and lower the interfacial tension between two liquids.
Regular solutionA regular solution is a solution that diverges from the behavior of an ideal solution only moderately.
Margules functionA Margules function is a function added to the Raoult's law description of a liquid solution to account for deviations from ideality.
Cryoscopic constantThe cryoscopic constant allows one to relate molality to freezing point depression.
Ebullioscopic constantThe ebullioscopic constant allows one to relate molality to boiling point elevation.
Tyndall effectThe Tyndall effect is the effect of light scattering on particles in colloid systems, such as suspensions or emulsions.
Eutectic pointAn eutectic mixture is a mixture at such proportions that the melting point is as low as possible, and that furthermore all the constituents crystallize simultaneously at this temperature from molten liquid solution.

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