Chapter 9C - Volumetric Analysis

• quantitative technique • involves measuring volume of a solution of known concentration to determine the concentration of the analyte • titration process

• Preperation of a standard solution using a primary standard • Titration b/w standard solution & solution to be standardised • Titration b/w standardised solution & solution being analysed • Stochiometric calculations to determine the concentration of the solution being analysed

• used for measuring a fixed volume (commonly 100 or 250mL) • used to prepare a standard solution (known concentration) • rinse with distilled water

• used for measuring a fixed volume (aliquot) • commonly 20 or 25mL • used to transfer a known volume of the solution being analysed to the conical flask • rinse with the solution it is to contain

• measure a variable volume (titre) • holds up to 50mL • usually contains the standard solution (known concentration) • rinse w/ the solution it is to contain

• amount of solute in a specified volume of solvent/solution

• used for holding the aliquot delivered from the pipette • rinse w/ distilled water

• amount of substance (mol) per volume of solution (L)

• %m/m • mass of component (g) per 100g sample/solution

• %v/v • volume of solute (mL) per 100mL solution

• %m/v • mass of solute (g) per 100mL solution

• mass of solute (mg) per kg of solution • mass of solute (mg) per L of solution

• solution w/ accurately known concentration • prepared in volumetric flask • prepared using a primary standard

• available in pure form • has a known formula • is stable enough to not react w/ atmosphere or decompose over time • reasonably high molar mass to minimise weighting errors • inexpensive

A standard solution is used to standardise another solution

Involves adding one solution (oxidant/reductant) to another solution (oxidant/reductant) until the reaction b/w them is complete

Point at which the ratio of oxidising agent to reducing agent present is equivalent to the stochiometric mole ratios in the equation

When the reaction solution changes colour (due to the indicator or one of the chemicals involved in the redox reaction)

• Rinse & fill a pipette w/ the analyte. Transfer aliquot to a conical flask • Add several drops of a suitable indicator to the conical flask if the reaction is not self indicating • Rinse & fill a burette w/ standard solution. Record initial burette reading • Titrate analyte w/ known solution until endpoint reached. Record final burette reading and titre • Repeat until 3 concordant titres obtained

• 0.1mL b/w lowest & highest titre • increases reliability/precision • minimises effect of random errors

• rinsing errors • indicator errors

• lead to overestimations or underestimations of the final analyte concentration

• decrease reactant amount (in mol) in the aliquot delivered to the conical flask • decreases size of titre • underestimated concentration

• increase reactant amount (in mol) in the aliquot delivered to the conical flask • increases size of titre • overestimated concentration