3.2 Volumetric Analysis

Strong acid/Strong base Strong acid/ weak base Weak acid/strong base

Volumetric analysis is a common laboratory technique used to determine the number of moles of reactants involved in a reaction

In a titration volumes of 2 solutions (one of a known concentration) are mixed together until the number of moles of each reaction are in the ratio shown by the balanced chemical equation. This is known as the equivalence point and is usually identified using an indicator which changes colour the moment this ratio is achieved.

A standard solution is a solution of precisely known concentration

1000cm³

A pipette is used to transfer a fixed volume of solution usually 25cm³

A burette is used to add variable volumes of a solution and it measures by difference. It should be filled using a funnel

A graduated flask is used to make up a solution of known concentration by dissolving a weighed amount of solid or volume of liquid in a fixed volume, usually 250cm³. Dissolve solids in a beaker first before transferring to the graduated flask .

The conical flask is used to carry out the reaction ( the location where one solution is added to the other). Normally the first solution is transferred using a pipette and an indicator is added, then the second solution is added from the burette until the indicator colour shows that the reaction is complete.

1) Weigh out the solid or liquid needed to the nearest 0.01 g in a beaker using a top pan balance 2) Dissolve the solid or liquid in a small amount of distilled water stirring to help it dissolve (do not use more tha 100cm³) 3) Rinse the stirring rod and add the washings to the beaker 4) Transfer the contents of the beaker to a 500cm volumetric flask through a filter funnel 5) rinse the beaker well making sure all the liquid goes into the flask and finally rinse the funnel 6) Add distilled water to the volumetric flask, swirling at intervs to mix the contents, until the level is within about 1cm of the mark at the neck of the flask 7) using a dropping pipette, add enough water to bring the bottom of the meniscus to the mark 8) Insert the stopper and invert the flask to ensure complete mixing and so that a homogenous solution is achieved

Hydrochloric acid and sulfuric acid

Sodium hydroxide and Potassium hydroxide

Ethanoic acid and citric acid ?

Ammonia and sodium carbonate

Phenolphthalein or Methyl orange

Methyl orange cannot be used if a weak acid is involved

Colourless to pink

Red to yellow