Acid-Base Titrations

• Acid-base titrations involve the neutralisation of an acid with a base in order to determine the concentration and ratio of the acid to the base.
• The apparatus required for this procedure includes a burette, pipette, conical flask and often a white tile for clearer visualisation of the colour change.
• A common indicator used in acid-base titrations is phenolphthalein, but the choice of indicator can vary depending on the strength of the acid and base being used.
• Phenolphthalein exhibits a pink colour in basic solutions and is colourless in acidic environments, making it useful for indicating the endpoint of the titration – when it changes from pink to colourless.
• To carry out a titration, start by measuring a known volume of solution (either the acid or base) into the conical flask with the pipette. The other solution is then carefully added from the burette.
• Titrations often require a rough, first trial to get a general idea of the volume required to reach the endpoint, followed by more precise trials for accurate results.
• During the addition of solution from the burette, constantly swirl the conical flask to ensure thorough mixing of the two solutions.
• Aim to slow the addition and drip the solution from the burette towards the endpoint to avoid overshooting the colour change.
• Once the endpoint is reached, measure the volume of solution added from the burette. This is known as the titration volume.
• You can calculate the concentration of the unknown solution using the formula n= CV where n is the number of moles, C is the concentration and V is the volume.
• By comparing the quantities of acid and base in the balanced chemical equation, you can determine their molar ratio.
• The closer the value of the calculated concentration to the true concentration, the more accurate the titration procedure.

Remember that meticulous technique and careful recording of all measurements and observations are critical to the success of an acid-base titration. Also be aware of sources of error, such as not cleaning the apparatus properly, or the indicator not changing at the exact point of neutralisation.