Introduction

A titration or volumetric analysis is a technique used in the Science laboratory to mix precise amounts of two solutions, one of which the concentration is known. By knowing the concentration of the standard solution being used, and by carefully measuring the volume of the second solution, we can determine the concentration of the second solution.

In class we have started to titrate a standard 0.103 mol/L solution of sodium hydroxide against a solution of hydrochloric acid. You carefully pipetted 25 mL of the dilute hydrochloric acid solution and placed this in a conical flask. You added a known number of drops of phenolphthalein indicator. When you add the standard sodium hydroxide solution in the burette, the indicator will turn permanent pale pink when the titration has reached the end point. The titre value is the volume of sodium hydroxide used each time to reach the end point. For Excellence level you need to have at least three titre values within a 0.20mL range of one another.

Titration Calculations

For this worked example you will be provided with titration results.

Worked Example 1

A student placed 25.0 mL aliquots of a solution of hydrochloric acid into a conical flask. Using phenolphthalein as an indicator, they titrated it against standardised 0.103 mol/L sodium hydroxide solution.