Standardization of 0.1 N Silver Nitrate (AgNO3)

ARGENTOMETRY

Any titration that uses silver nitrate as standard is termed as

reagent-grade sodium chloride

primary standard (5% moisture, requires drying)

Eosin Y

the adsorption indicator used.

Eosin Y

It provides a sharp endpoint in acidic media (the color

change is sharpest in an acetic acid solution).

acetic acid

is used to sharpen the

endpoint.

Eosin Y

_ however can compete with the chloride ions to react with the silver ions.

silver

If eosin Y reacts

first with _, there will be a premature determination of the endpoint.

chloride

All _ ions (from

sample NaCl) must react first with silver ions (from AgNO3) before Eosin Y.

Methanol

_ is added to

prevent this competition.

Alcohol

_ is used in the assay to help keep the precipitated silver

chloride in a colloidal state and thus give sharpness to the color change which occurs on

the precipitate surface.

magenta

The color of the precipitate of eosin Y with silver is _.

magenta

So the color of the precipitate of AgCl (white) changes to _ (endpoint).

AgNO3

must be protected from sunlight

precipitate

The _ should separate as far as possible in the solution.

RULES ON THE USE OF ADSORPTION INDICATOR

• The precipitate should separate as far as possible in the solution. Large quantities of neutral salts (with different charges) should be avoided owing to their precipitating effect.

• The indicator ion must have an opposite charge to the ion of the precipitating agent (AgNO3).

• The indicator ion should not be adsorbed before the particular compound has been completely precipitated, but it should be strongly adsorbed immediately after the equivalence point.

neutral salts

Large quantities of _ (with different charges) should be avoided owing to their precipitating effect.

indicator

The _ ion must have an opposite charge to the ion of the precipitating agent (AgNO3).

precipitating agent

The indicator ion must have an opposite charge to the ion of the _ (AgNO3).

indicator

The _ ion should not be adsorbed before the particular compound has been completely precipitated, but it should be strongly adsorbed immediately after the equivalence point.

equivalence point

The indicator ion should not be adsorbed before the particular compound has been completely precipitated, but it should be strongly adsorbed immediately after the _.

precipitated

The indicator ion should not be adsorbed before the particular compound has been completely _, but it should be strongly adsorbed immediately after the equivalence point.