Vocabulary  for Standard 6  Solutions

 

Word

 

Definition

Boiling-point elevation

 

The boiling point of a solution is higher than the boiling point of the pure solvent. Boiling point elevation is a colligative property

Chromatography

 

Chromatography is a method for separating mixtures based on differences in the speed at which they migrate over or through a stationary phase

Colligative properties

 

Properties of a solution that depend on the number of solute molecules present, but not on the nature of the solute. Osmotic pressure, vapor pressure, freezing point depression, and boiling point elevation are examples of colligative properties.

Colloid

 

A colloid is a heterogeneous mixture composed of tiny particles suspended in another material. The particles are larger than molecules but less than 1 µm in diameter. Particles this small do not settle out and pass right through filter paper. Milk is an example of a colloid. The particles can be solid, tiny droplets of liquid, or tiny bubbles of gas; the suspending medium can be a solid, liquid, or gas (although gas-gas colloids aren't possible).

Concentration

 

1. A measure of the amount of substance present in a unit amount of mixture. The amounts can be expressed as moles, masses, or volumes. 2. The process of increasing the amount of substance in a given amount of mixture.

Dissociation

 

When ionic substances dissolve, their ions are surrounded by solvent molecules and separated from each other. This phenomena is also called ionization.

dissolution    
dissolve    
dissolved    

Distillation

 

Distillation is a technique for separating components of a mixture on the basis of differing boiling points. The mixture is heated, vaporizing some of the components. The vapor is collected and condensed to isolate the components with the lowest boiling points.

Electrolyte

 

A substance that dissociates fully or partially into ions when dissolved in a solvent, producing a solution that conducts electricity. See strong electrolyte, weak electrolyte.

Enthalpy of solution

 

The heat absorbed or released when a solute is dissolved in a solvent. The heat of solution depends on the nature of the solute and on its concentration in the final solution.

Freezing-point depression

 

The freezing point of a solution is always lower than the freezing point of the pure solvent. The freezing point depression is roughly proportional to the molality of solute particles in the solution. Freezing point depression is an example of a colligative property of a solution.

Henry’s Law

 

Henry's law predicts that the solubility (C) of a gas or volatile substance in a liquid is proportional to the partial pressure (P) of the substance over the liquid:

P = k C

where k is called the Henry's law constant and is characteristic of the solvent and the solute.

Hydration

 

Combination with water.

Hydronium ion

(H3O+) hydronium.

The H3O+ ion, formed by capture of a hydrogen ion by a water molecule. A strong covalent bond is formed between the hydrogen ion and water oxygen; all hydrogen ions in aqueous solution are bound inside hydronium ions.

Immiscible

immiscibility.

Two liquids are considered "immiscible" or unmixable if shaking equal volumes of the liquids together results in a meniscus * visible between two layers of liquid. If the liquids are completely immiscible, the volumes of the liquid layers are the same as the volumes of liquids originally added to the mixture.

Ionization

 

 

Miscible

miscibility; liquid miscibility.

Two liquids are considered "miscible" or mixable if shaking them together results in a single liquid phase, with no meniscus visible between layers of liquid.

Molality

(m)

Concentration measured as moles of solute per kilogram of solvent. For example, a 1 m NaCl solution contains 1 mole of NaCl per kilogram of water. Molalities are preferred over molarities in experiments that involve temperature changes of solutions, e. g. calorimetry and freezing point depression experiments.

Molarity

(M) molar concentration.

Concentration of a solution measured as the number of moles of solute per liter of solution. For example, a 6 M HCl solution contains 6 moles of HCl per liter of solution.

Net ionic equation

 

A net ionic equation is an ionic equation with all DEFINE[spectator ions">spectator ions eliminated. For example, Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) = AgCl(s) + Na+(aq) + NO3-(aq) is an ionic equation; the net ionic equation would be Ag+(aq) + Cl-(aq) = AgCl(s) because the sodium and nitrate ions are spectators (they appear on both sides of the ionic equation.

Nonelectrolyte

 

A nonelectrolyte is a substance which does not ionize in solution.

Parts per million

parts of solute per million, ppm

Concentration expressed as parts of solute per million parts of solution. Usually refers to parts per million by mass. For example, a 10 ppm NaCl solution can be written as: 10 mg NaCl/kg solution, 10 µg NaCl/g solution, 10 ng NaCl/mg solution. In very dilute aqueous solutions, ppm is approximately equal to mg solute per liter of solution.

random molecular motion    

Saturated solution

 

A solution which does not dissolve any more solute. When a saturated solution is placed in contact with additional solute, solute neither dissolves nor is deposited from a saturated solution.

Solubility

solubilities; equilibrium solubility; solubleness.

The solubility of a substance is its concentration in a saturated solution. Substances with solubilities much less than 1 g/100 mL of solvent are usually considered insoluble. The solubility is sometimes called "equilibrium solubility" because the rates at which solute dissolves and is deposited out of solution are equal at this concentration.

Soluble

 

Capable of being dissolved in a solvent (usually water).

Solute

 

A substance dissolved in a solvent to make a solution.

Solution

homogeneous mixture.

A sample of matter consisting of more than one pure substance with properties that do not vary within the sample. Also called a homogeneous mixture.

Solvent

 

The most abundant component in a solution.

Spectator ions

 

A spectator ion is an ion that appears as both a reactant and a product in an ionic equation. For example, in the ionic equation

Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) = AgCl(s) + Na+(aq) + NO3-(aq)

the sodium and nitrate ions are spectator ions.

Strong electrolyte

 

A strong electrolyte is a solute that completely dissociates into ions in solution. Solutions of strong electrolytes conduct electricity. Most soluble ionic compounds are strong electrolytes.

Supersaturated solution

supersaturated

A supersaturated solution has concentration of solute that is higher than its solubility. A crystal of solute dropped into a supersaturated solution grows; excess solute is deposited out of the solution until the concentration falls to the equilibrium solubility.

Suspension

 

A heterogeneous mixture in which droplets or particles are suspended in a liquid.

Unsaturated solution

 

A solution with a concentration lower than its equilibrium solubility.

Weak electrolyte

 

A weak electrolyte is a solute that incompletely dissociates into ions in solution. For example, acetic acid partially dissociates into acetate ions and hydrogen ions, so that an acetic acid solution contains both molecules and ions. A solution of a weak electrolyte can conduct electricity, but usually not as well as a strong electrolyte because there are fewer ions to carry the charge from one electrode to the other.