Anachem: Volumetric/Titration

what are the requirements for volumetric analysis? (4)

A.) Accurate balance with which to weigh materials for analysis

B.) Graduated instruments to measure volumes of solutions used

C.) Standard Solutions

D.) Indicators

What are the conditions to be met for volumetric analysis?

1) The reaction between standard and sample must be rapid

2) No side reaction should occur

3) The reaction must be complete

4) There should be an abrupt change in some properties at or near the equivalence point.

5) An indicator should be available

Volumetric Analysis

involves dissolving a weighed amount of sample and titrating the resulting solution with a standard solution.

titration

is the progressive addition of a standard solution with which is reacts

standard solutions

solution of accurately known concentration

standardization

the process of determining the concentration of a standard solution

Standardization may be carried out in three ways:

1. Direct Standardization

2. Titration of a weighted portion

3. Titration of a measured volume

Direct standardization

of a standard solution by dissolving a weighed amount of pure dry chemical and diluting the solution to an exactly measured volume.

e.g. 1 M AgNO3 : weighed 169.89 g of pure AgNO3 then add water to give exactly 1.000L of solution

primary standardization

Titration of a weighed portion of pure dry chemical by the solution to be standardized.

-a pure dry solid substance of known chemical composition used in the direct standardization of solution

secondary standardization

Titration of a measured volume of a solution that has itself been standardized previously

what are the 2 types of titration?

1. Direct

2. Indirect

Direct Titration (Dead Stop)

the standard solution is titrated directly with the sample in question

Indirect Titration

an excess of reagent is added to the sample in question and the excess reagent is titrated with another standard solution.

types of volumetric methods (4)

1. Neutralization methods a. Acidimetry - an acid is titrated with a standard solution of a base

b. Alkalimetry - a base is titrated with a standard solution of an acid

2. Redox methods

a. Permanganate titrations

b. Dichromate and ceric titrations

c. Iodimetry

3. Volumetric Precipitation titrations or precipitimetry

4. Compleximetric titrations or compleximetric

Titer

is the weight of substance that is chemically equivalent to one mL of the solution.

E.g. A silver nitrate solution has a KCl titer of 1.00 mg. This means that one mL of the AgNO3 solution is chemically equivalent to 1.00 mg of KCl.

methyl orange

pH 3-4 red to yellow

methyl red

pH 4-6 red to yellow

phenolphthalein

pH 8-10 colorless to pink

standard solution for acids

1. HCl

2. Sulfuric Acid

3. Perchloric Acid

standard solution for base

1. NaOH

2. KOH

3. Barium hydroxide

primary standards for acids

1. Sodium Carbonate

2. Calcium Carbonate

3. THAM - Tris (hydroxymethyl)

4. Amino Methane (CH2OH)C•NH2

Primary Standard for Base

1. Potassium Acid Phthalate (KHP or KHC8H4O4)

2. Benzoic Acid