analytical chemistry exam 2

Hardness of Water

contains calcium, magnesium, and heavy metal ions that form precipitates with soap.

Masking agent

a complexing agent that reacts selectively with a component in a solution to prevent that component from interfering in a determination.

Ligand

An ion or molecule that forms a covalent bond with a cation or a neutral metal atom by donating a pair of electrons, which are then shared by the two.

Chelate

Produced when a metal ion coordinates with two or more donor groups of a single ligand to form a 5 or 6 membered ring.

Zwitterion

The species that results from the transfer in solution of a proton from an acidic group to an acceptor site on the same molecule.

EDTA

ethylenediaminetetraacetic acid

Conditional Formation constants

pH dependent, used to calculate equilibrium concentration of the metal ion and the complex at equivalence point and where there is excess of reactant.

Tetradentate chelating agent

Coordination number

Reducing agent

an electron donor

Oxidizing agent

electron acceptor

Electrochemical cell

oxidizing and reducing agents are physically separated from each other with a salt bridge.

Salt bridge

Isolates reactants but maintains electrical contact in a cell

Potential

Voltage

potential difference between two electrodes

Cells without liquid junction

electrodes in some cells that share a common electrolyte.

Cathode

where reduction occurs

anode

where oxidation occurs

Galvanic cells

store electrical energy

electrolytic cells

consume electricity

Batteries

cells in series that produce higher voltages than a single

Electrolytic cell

requires external source of electrical energy

Reversible cell

Reversing current reverses the reaction

Irreversible cell

reversing current causes different half reactions to occur

Liquid junction potential

result of the difference in the rates at which ions in the cells and salt bridge migrate

Interface

Phase boundary between the electrode and its solution

Standard state

reference state from which relative values are calculated. Differs for gas/liquid/solid

Standard cell potential

Occurs when reactants and products are in their standard states

Plus right rule

the positive lead ought to be connected to the right-hand electrode

Standard hydrogen electrode (SHE)

The reference half-cell electrode

Platinized

Metal conductor coated with finely divided platinum to increase surface area.

Electrode potential

potential of cell with right-hand electrode in question and left-hand SHE.

Standard Electrode Potential

electrode potential when activities of the reactants and products are in unity

Formal Potential

electrode potential when ratio of analytical concentrations of reactants and products of half-reaction is 1.00, and molar solute concentrations are specified.

1, 10-phenathroline

form stable complexes with iron(II) and other ions.

Electrode Potential

Ecell = Erh-Elh

equilibrium in a redox reaction

the electrode potentials are identical.

Redox equivalence point

Eeq= Eo - .0592/n log (products/reactant)

inverse master equation

Redox indicators

substances that change color when oxidized or reduced.

System Potential

short-circuit

two halves of a cell are connected directly with a wire so electrons can freely pass.