Unit 4 Flashcards
(43 cards)
What is a Solution?
A solution is a homogeneous mixture of two or more substances where the particles are evenly distributed at the molecular level.
What are the Components of a Solution? Explain.
Solvent:
The substance present in the larger amount.
Determines the phase of the solution (solid, liquid, gas).
Example: In saltwater, water is the solvent.
Solute:
The substance present in a smaller amount.
Dissolves in the solvent.
Can be a solid, liquid, or gas.
Example: In saltwater, salt is the solute.
Explain Like Dissolves Like.
Polar and Nonpolar:
Polar substances dissolve in polar solvents.
Nonpolar substances dissolve in nonpolar solvents.
Example:
Polar solute + Polar solvent: Salt dissolves in water.
Nonpolar solute + Nonpolar solvent: Oil dissolves in hexane.
Polar solute + Nonpolar solvent: No dissolution (e.g., salt in oil).
Explain the Formation of a Solution.
Solvent-Solute Interaction:
For a solution to form, solute-solvent attractions must overcome solute-solute and solvent-solvent attractions.
Dissolution:
Solute particles disperse among solvent particles.
What Are Electrolytes?
Electrolytes are substances that dissolve in water to produce ions, enabling the solution to conduct electricity.
Explain Strong Electrolytes.
Definition: Substances that completely dissociate into ions in water.
Dissolve and fully break into cations and anions.
Conductivity: Solutions conduct electricity well due to the high concentration of ions.
Explain Weak Electrolytes.
Definition: Substances that only partially dissociate in water.
Partially dissociate into ions and molecules. Double arrows indicate equilibrium between dissociated and undissociated forms.
Conductivity: Weakly conductive because only a small fraction of molecules form ions.
Explain Nonelectrolytes.
Definition: Substances that dissolve in water but do not form ions.
Dissolve without breaking into ions.
Conductivity: Do not conduct electricity because no ions are present.
How to Identify Strong Electrolytes
Strong Electrolytes:
Ionic compounds containing:
Group 1 cations (e.g., Na⁺, K⁺).
Group 2 cations (e.g., Ca²⁺, Mg²⁺).
Halide anions (e.g., Cl⁻, Br⁻, I⁻).
Strong acids: HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄.
Strong bases: NaOH, KOH, Ba(OH)₂.
How to Identify Weak Electrolytes
Weak Electrolytes:
Weak acids: Look for a compound with H that doesn’t completely dissociate (e.g., acetic acid, CH₃COOH).
Weak bases: Ammonia (NH₃) and other compounds that slightly ionize in water.
How to Identify Nonelectrolytes
Nonelectrolytes:
Covalent compounds that dissolve without ionizing:
Sugars (e.g., glucose, sucrose).
Alcohols (e.g., ethanol, methanol).
Other organic molecules.
Explain Electric Conductivity.
Solutions with more ions (strong electrolytes) are better conductors of electricity.
Solutions with few or no ions (weak electrolytes and nonelectrolytes) are poor or non-conductors.
How to Identify the Equivalents for a Solution
What is Solubility?
Definition: Solubility is the maximum amount of a solute that can dissolve in a given amount of solvent (typically 100 g of water) at a specific temperature.
Explain a Saturated Solution.
Contains the maximum amount of solute that can dissolve at a given temperature.
Any additional solute will not dissolve and will settle at the bottom.
Explain a Unsaturated Solution.
Contains less solute than the solvent’s maximum capacity to dissolve.
More solute can be added and dissolved.
Explain a Supersaturated Solution.
Contains more solute than the solvent can typically dissolve.
Formed by dissolving solute at a high temperature and then cooling the solution slowly.
These solutions are unstable, and the excess solute can crystallize out.
How Does Temperature Affect Solubility?
Solids in Liquids:
Solubility increases with temperature.
Example: More sugar dissolves in hot water than in cold water.
Gases in Liquids:
Solubility decreases with temperature.
Example: Soda loses carbonation faster at room temperature because CO₂ escapes more easily.
What is Concentration?
Concentration measures how much solute is present in a given quantity of solution or solvent. It indicates how “strong” or “dilute” a solution is.
Explain a Dilute Solution.
Contains a small amount of solute relative to the solvent
Explain a Concentrated Solution.
Contains a large amount of solute relative to the solvent.
How to Calculate Mass Percent (m/m) Concentration.
How to Calculate Volume Percent (v/v) Concentration.
How to Calculate Mass/Volume Percent Concentration.
