bbst026

8/18/2006

Final Assignment 2

Most S.4 Chemistry Students do not know why the end point of an acid-base titration (e.g. colour change of the indicator) can roughly match the equivalence point of the titration. From the following learning object, it shows when various amount of hydrochloric acid (acid) is added into sodium hydroxide solution (base), the pH of the reaction mixture (indicated by the titration curve) and colour of the indicator (in this case : methyl orange) at each particular moment. The visual representation can make the case explicitly visualize to the students.

How to use it

When adding different volumes of hydrochloric acid (HCl) into sodium hydroxide solution (NaOH) by dragging slider from left to right, the pH value of the reaction mixture can be shown on the titration curve and the colour of the indicator (methyl orange) can be shown simultaneously on the conical flask.

The presentation can show that the end point of the titration (the indicator changes its colour from yellow to red) is very close to the equivalence point of the titration (10 mL). It makes students clear why the end point of the titration can be used to replace the equivalence point of the titration in volumetric analysis calculation.

My presentation Flash file is placed on http://iln.cite.hku.hk/com/1238/users/wmlam/Titration2.fla