Analytical Chemistry Exam #2

Volumetric analysis

the volume of a known reagent required for complete reaction with analyte by a known reaction is measured

Titration

a procedure in which increments of a known reagent are added to analyte until the reaction between analyte and titrant is complete

Titrant

the known reagent used in a titration

Indicator

a compound with a physical property (usually color) that changes abruptly when the titration is complete.

Equivalence Point

the point when the quantity of titrant added is the exact amount necessary for stoichiometric reaction with the analyte; ideal result

End point

marked by a sudden change in a physical property of the solution; what we actually measure

Titration error

The difference between the end point and the equivalence point

Blank titration

the same procedure of titrating is carried out without the analyte to estimate the titration error

Primary standard

a reagent that is pure enough to weigh out and use directly to provide a known number of moles; should be 99.9% pure or better

Standardization

The process of titrating a standard to determine the concentration of titrant

Standard solution

a solution whose concentration is known

Direct titration

titrant is added to analyte until the end point is observed

Back titration

known excess or a standard reagent is added to the analyte, then a second standard reagent is used to titrate the excess of the first reagent

Solubility product

the equilibrium constant for the reaction in which a solid salt (ionic compound) dissolves to give its constituent ions in solution

Saturated

a solution that contains all the solid capable of being dissolved

Common ion effect

A salt is less soluble if one of its constituent ions is already present in the solution

Bronsted Lowry acid

a proton donor

Bronzed Lowry base

a proton acceptor

Autoprotolysis

self ionization

Strong acids

HCl

HBr

HI

H2SO4

HNO3

HClO4

Strong bases

LiOH

NaOH

KOH

RbOH

CsOH

R4NOH

Reagent

Titrant

Titer value

Titrand

Analyte

Primary Standard Requirements

Easy to obtain high purity

Unaffected by air

Known and stable composition

High MM

Readily soluble

Reaction with analyte is complete

Buffered solution

Resists changes in pH when small amounts of acids or bases are added or when it is diluted

Buffer

Consists of a mixture of a weak acid and it's conjugate base

Buffer capacity

Measures how well a solution resists changes in pH when acid or base is added

Buffer capacity maximum

pH=pKa

Acid

Substance that increases the concentration of hydronium ion

Base

Decreases the concentration of hydronium ion in an aqueous solution

Masking agent

Prevents impurities from reacting with the precipitant

chelating agent

molecules or ions that can attach itseld to the metal ion through more than one atom

chelating effect

the ability of multidentate ligands to form more stable metal complexes than those formed by similar monodentate ligands

chelating ligand

a ligand that binds to a metal through more than one atom