뒤로Solutions and Solubility in GOB Chemistry
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Solutions
Definition and Properties
A solution is a homogeneous mixture composed of at least one solute uniformly dissolved in a solvent. The physical state of the solution is determined by the state of the solvent. Solutions can involve solutes and solvents in any physical state (solid, liquid, or gas).
Solute: The substance dissolved in the solvent.
Solvent: The substance in which the solute is dissolved; determines the phase of the solution.
Types of Liquid Mixtures
Liquid mixtures can be classified based on their homogeneity and particle size:
Solution: Homogeneous, transparent, not easily separable (e.g., salt in water).
Colloid: Heterogeneous, opaque, not easily separable (e.g., milk, mayonnaise).
Suspension: Heterogeneous, opaque, easily separable (e.g., blood, matcha).
Dissolving and Solubility
Dissolving Process
Dissolving is a physical process where a solute in any phase (gas, liquid, or solid) dissolves in a solvent to form a solution. For ionic compounds, this involves dissociation into ions.
Example: Dissolving NaCl in water:
Writing Dissociation Equations: For MgCl2:
For K3PO4:
Solubility and Predicting Solubility
Solubility is the ability of a solute to dissolve in a solvent. The rule of thumb is "like dissolves like":
Polar solute + Polar solvent = Soluble
Nonpolar solute + Nonpolar solvent = Soluble
Polar solute + Nonpolar solvent = Insoluble
Example: Oil (nonpolar) and water (polar) are insoluble.
Solubility Rules for Ionic Compounds in Water
Solubility rules help predict whether an ionic compound will dissolve in water. Ionic compounds are usually soluble if they contain certain ions.
Positive Ions | Negative Ions |
|---|---|
Li+, Na+, K+, Rb+, Cs+, NH4+ | NO3-, C2H3O2- |
Cl-, Br-, I- (except with Ag+, Pb2+, or Hg22+) | |
SO42- (except with Ba2+, Pb2+, Ca2+, Sr2+, or Hg22+) |
Ionic compounds that do not contain at least one of these ions are usually insoluble.
Electrolytes
Definition and Classification
Electrolytes are substances that produce ions when dissolved in water, allowing the solution to conduct electricity. They are classified based on their degree of ionization:
Type of Solute | Examples |
|---|---|
Strong electrolyte | Ionic compounds (NaCl, KBr, MgCl2, NaNO3), strong bases (NaOH, KOH), strong acids (HCl, HBr, HI, HNO3, HClO4, H2SO4) |
Weak electrolyte | HF, H2O, NH3, HC2H3O2 (acetic acid) |
Nonelectrolyte | Carbon compounds (CH3OH, C2H5OH, C12H22O11, CH4N2O) |
Concentration of Solutions
Concentration Expressions
The concentration of a solution is the amount of solute per amount of solution. Common expressions include:
Mass Percent (m/m):
Volume Percent (v/v):
Mass/Volume Percent (m/v):
Molarity (M):
Dilution
Dilution is the process of reducing the concentration of a solute by adding more solvent. The relationship is given by:
Where and are the initial concentration and volume, and and are the final concentration and volume.
Osmosis
Definition and Biological Importance
Osmosis is the movement of water through a semipermeable membrane from a region of low solute concentration to high solute concentration. Osmosis occurs only with solutions, not colloids or suspensions, due to particle size.
Isotonic: Equal concentration of solute inside and outside the cell.
Hypotonic: Lower solute concentration outside the cell; cell swells.
Hypertonic: Higher solute concentration outside the cell; cell shrinks.
Additional info:
Hydrogen bonding is a special type of intermolecular force occurring between hydrogen and highly electronegative atoms (N, O, F), contributing to solubility and solution properties.
