Understanding Solutions and Their Classifications

• A solution is a mixture of two or more substances in a single phase.
• Solutions consist of a solute, which is the part being dissolved, and a solvent, which dissolves the solute.
• The equation for a solution is Solute + Solvent = Solution.

5 Classifications of Solutions

• Miscibility
• Saturation
• Heat absorption or evolution during formation
• Relative amount of solute
• Concentration in relation to a certain standard

Based on Miscibility

• Miscible: Two liquids that dissolve in each other in any proportion, such as water and alcohol.
• Partially Miscible: Two liquid components forming a single phase when mixed in certain proportions, but form two phases when mixed in different proportions, like benzene and water.
• Immiscible: Two components that are insoluble in each other, such as water and mercury.

Based on Saturation

• Saturated solution: Contains the maximum quantity of solute that dissolves at a specific temperature.
• Unsaturated solution: Contains less than the maximum amount of solute that can dissolve at a particular temperature.
• Supersaturated solution: Contains more solute than a solvent can dissolve at a given temperature.

Based on Heat Absorbed or Evolved in Formation

• Exothermic solution: Evolution of heat during formation causes the solution to become hot, such as NaOH in water.
• Endothermic solution: Absorption of heat during formation causes the solution to become cold.
• Preparation of ethyne is an exothermic reaction of water and calcium carbide.
• Endothermic reactions include those of Barium Hydroxide and Ammonium Salts.

Based on Relative Amount of Solute Present

• Dilute solution: Contains a relatively small amount of solute.
• Concentrated solution: Contains a relatively large amount of solute.

Based on the Concentration in Relation to a Certain Standard

• Isotonic solution: Has the same concentration as the standard, like Normal Saline Solution (0.85 – 0.9% NaCl) with the salt concentration in blood.
• Hypotonic Solution: Has a concentration lower than the standard.
• Hypertonic Solution: Has a concentration greater than the standard.

Properties of Solutions

• Homogeneity: Uniform throughout, meaning the composition is the same at all points within the mixture.
• Particle Size: Particles are very small, often at the molecular or ionic level.
• Solubility: The ability of a substance to dissolve in a particular solvent under specific conditions.
• Concentration: The amount of solute dissolved in a given amount of solvent.
• Colligative Properties: Solutions exhibit these properties, which depend on the number of solute particles.
• Boiling Point Elevation and Freezing Point Depression: Adding a solute to a solvent typically increases the boiling point and decreases the freezing point.
• Osmosis and Osmotic Pressure: Osmosis is the movement of solvent molecules across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration.
• Conductivity: Aqueous solutions of ionic compounds can conduct electricity due to the presence of ions.
• Color and Transparency: The color depends on the nature of the solute and solvent.
• Saturation: The solution contains the maximum amount of solute that can dissolve at a particular temperature and pressure.

Solubility Rules in Water

• All common compounds of Group I and ammonium ions are soluble, including Li+, Na+, K+, Cs+, and Rb+.
• All nitrates, acetates, and chlorates are soluble.
• Soluble compounds include Sodium Nitrate (NaNO3), Aluminum acetate (Al(CH3CO2)3), and Sodium perchlorate (NaClO4).
• All binary compounds of the halogens (other than F) with metals are soluble, except those of Ag, Hg(I), and Pb.
• Examples include Sodium iodide (NaI) and Potassium iodide (KI).
• All sulfates are soluble, EXCEPT those of barium, strontium, calcium, lead, silver, and mercury (I).
• Soluble sulfates are Sodium sulfate (Na2SO4) and Beryllium sulfate (BeSO4).
• Most carbonates, hydroxides, oxides, silicates, and phosphates are insoluble.
• Sodium carbonate (Na2CO3), Lithium Hydrides (LiH), and Sulfur Oxides (SO) are examples.
• Sulfides are insoluble except for calcium, barium, strontium, magnesium, sodium, potassium, and ammonium.
• Examples include Calcium sulfide (CaS) and Potassium sulfide (K2S).

Soluble or Insoluble in Water

• PbSO4 is insoluble
• BaCO3 is insoluble
• Li3PO4 is insoluble
• FeS is insoluble
• Ca(OH)2 is soluble
• Co(NO3)3 is soluble

Factors Affecting Solubility

• Nature of Solvent and Solute: "Like Dissolves Like": Polar solvents tend to dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes.
• Effect on Solid Solutes: The solubility of solid solutes in liquids generally increases with an increase in temperature.
• Effect on Gaseous Solutes: The solubility usually decreases with increasing temperature.
• Effect on Solids and Liquids: Pressure has a minimal effect on the solubility of solids and liquids in liquids.
• Effect on Gases: Henry's law states that the solubility of a gas in a liquid is directly proportional to the gas's pressure above the liquid.

Solubilities of Solids vs. Temperature

• Solubilities of several ionic solids as a function of temperature.
• Most salts have greater solubility in hot water
• Some salts have a negative heat of solution, becoming less soluble with increasing temperature.
• The solubility of gases decreases at higher temperatures.

Henry's Law

• Describes the relationship between the partial pressure of a gas and its solubility in a liquid.
• William Henry, an English chemist, first formulated this principle in the early 19th century.
• c = kP, where c is the solubility of the gas (M), k is Henry's Law Constant, and P is the partial pressure of gas.
• Henry's Law Constants (25°C), k:
• N2: 8.42 •10-7 M/mmHg
• O2: 1.66 •10-6 M/mmHg
• CO2: 4.48•10-5 M/mmHg

Henry's Law & Soft Drinks

• Soft drinks contain "carbonated water," which is water with dissolved carbon dioxide gas.
• Drinks are bottled with a CO2 pressure greater than 1 atm.
• The pressure of CO2 decreases, and the solubility of CO2 also decreases when the bottle is opened.
• According to Henry's Law, bubbles of CO2 escape from the solution.

Factors That Speed Up the Rate of Solubility

• Particle Size: Smaller particles have a larger surface area, allowing more interactions with the solvent molecules.
• Mechanical agitation: Stirring or shaking the solution helps distribute solute particles throughout the solvent, reducing the concentration gradient.
• Higher temperatures: Solubility tends to increase with higher temperatures for many solutes.

Factors Affecting the Rate of Chemical Reaction

• The chemical identity determines the rate at which different substances react. Reactions proceed at various speeds based on the chemical properties of the reactants.
• Fluorine is the most active of the halogens and combines with Hydrogen with explosive violence
• Reactions favor greater contact and collision among molecules, which leads to increased reaction velocity.
• Higher temperatures generally increase the kinetic energy of particles.
• Catalysts are substances that speed up reactions without being consumed.
• Higher concentrations of reactants lead to more frequent collisions between particles, resulting in an increased reaction rate.