There are a number of ways that you could investigate neutralisation in Chemistry. This is an outline of the required steps to undertake one of these methods. Calcium oxide or calcium hydroxide can be used in this practical.
To investigate the change in pH when adding powdered calcium hydroxide to a fixed volume of dilute hydrochloric acid.
Record the results in a suitable table. For example:
|Number of spatulas added||pH of reaction mixture|
Plot a graph to show:
Make sure you choose suitable scales so that at least 50% of the graph area includes plotted points. Draw a curve of best fit through these points.
The diagram shows an example:
Use the graph to estimate the number of spatulas of calcium hydroxide needed to produce a neutral solution.
Six spatulas of calcium hydroxide were needed to produce a neutral solution (pH 7).
Suggest two ways in which more accurate results could be obtained.
You could measure the mass of calcium hydroxide powder using a balance. You could also use a pH probe and meter to measure the pH, rather than estimating it using universal indicator.
It is important in this practical activity to use appropriate apparatus and methods. This includes the safe use and careful handling of substances.
Evaluate the hazards and the precautions needed to reduce the risk of harm. For example:
|Hydrochloric acid||Concentrated acid is corrosive and damages skin and clothes||Use dilute hydrochloric acid|
|Calcium hydroxide powder||Causes skin irritation||Wear gloves|
|Calcium hydroxide powder||Causes serious eye damage||Wear eye protection|
|Calcium hydroxide powder||May cause respiratory irritation||Avoid making a dust|