Chapter 8: Reactions in Aqueous Solutions: Chemistry of the Hydrosphere

molarity

(M) The number of moles of solute per liter of solution: M = n/V ; also called molar concentration.

standard solution

A solution, used in chemical analysis, that contains an accurately known concentration of a solute.

dilution

The process of lowering the concentration of a solution by adding more solvent.

absorbance 

(A) A measure of the quantity of light that a sample absorbs.

beer’s law

The relation of the absorbance of a solution (A) to concentration (c), the light's path length (b), and the solute's molar absorptivity (ε) by the equation A = εbc .

molar absorptivity

(ε) A measure of how well a substance absorbs light.

calibration curve

A graph showing how a measurable property, such as absorbance, varies for a set of standard samples of known concentration that can later be used to identify an unknown concentration from a measured absorbance.

electrode

A solid electrical conductor used to make contact with a solution or other nonmetallic component of an electrical circuit.

electrolyte

A solute that produces ions in solution, enabling its solutions to conduct electricity.

strong electrolyte

A substance that dissociates completely when it dissolves in water.

nonelectrolyte

A molecular substance that does not ionize when it dissolves in water

hydronium ion

(H₃O⁺) A H⁺ ion plus a water molecule, H₂O; the form in which the hydrogen ion is found in an aqueous solution.

weak electrolyte

A substance that only partly ionizes when it dissolves in water.

acid (Brønsted–Lowry acid)

A proton donor.

base (Brønsted–Lowry base)

A proton acceptor.

neutralization reaction

A reaction that takes place when an acid reacts with a base and produces a solution of a salt in water

salt

The product of a neutralization reaction, made up of the cation of the base in the reaction plus the anion of the acid.

molecular equation

A balanced chemical equation describing a reaction in solution in which the reactants and products are written as neutral compounds.

overall ionic equation

A balanced chemical equation that shows all the species, both ionic and molecular, present in a reaction occurring in aqueous solution.

net ionic equation

A balanced chemical equation that describes the actual reaction taking place in aqueous solution; it is obtained by eliminating the spectator ions from the overall ionic equation.

spectator ion

An ion present in a reaction vessel when a chemical reaction takes place but that is unchanged by the reaction; spectator ions appear in an overall ionic equation but not in a net ionic equation.

strong acid

An acid that completely ionizes in aqueous solution.

weak acid

A weak electrolyte that only partially ionizes in aqueous solution.

carboxylic acid

A compound containing the –COOH functional group.

strong base

A base that completely dissociates into ions in aqueous solution.

weak base

A base that is a weak electrolyte and so has a limited capacity to accept protons.

amphiprotic

Describes a substance that can behave as either a proton acceptor or a proton donor.

titration

An analytical method of determining the concentration of a solute in a sample by reacting the solute with a solution of known concentration.

titrant

The standard solution added to the sample in a titration.

analyte

The substance whose concentration is to be determined in a chemical analysis

equivalence point

The point in a titration at which just enough titrant has been added to react with all the analyte in the sample.

end point

The point in a titration at which a color change or other signal indicates that enough titrant has been added to react with all the analyte in the sample.

precipitate

A solid product formed from a reaction in solution.

precipitation reaction

A reaction in which soluble reactants form a product that has limited solubility.

saturated solution

A solution that contains the maximum concentration of a solute possible at a given temperature.

unsaturated solution

A solution that contains less than the maximum quantity of solute predicted to be soluble in a given volume of solution at a given temperature.

supersaturated solution

A solution that contains more than the maximum quantity of solute predicted to be soluble in a given volume of solution at a given temperature.

oxidation

A chemical change in which an element loses electrons; the oxidation number of the element increases.

reduction

A chemical change in which an element gains electrons; the oxidation number of the element decreases.

oxidation number (O.N.) or oxidation state

A measure of the number of electrons an atom in a molecule or ion has compared to the number it would have if it were a free atom.

oxidizing agent

A reactant that accepts electrons from another in a redox reaction, thereby oxidizing the other reactant; the oxidizing agent is reduced in the reaction.

reducing agent

A reactant that donates electrons to another in a redox reaction, thereby reducing the other reactant; the reducing agent is oxidized in the reaction.

half-reaction

One of the halves of an oxidation–reduction reaction; one halfreaction is the oxidation component, and the other is the reduction component.

activity series

A high-to-low ranking of metals on the basis of their strengths as reducing agents.