Read through the whole investigation carefully, before beginning any practical work.
(a) Investigating the effect of pH on the rate of decomposition of hydrogen peroxide by catalase.
The experiment involves measuring the quantity of oxygen produced, using the
following method.
(i) Pour distilled water into a clean boiling tube until it is half full. Place the fine open end of the delivery tube into the water so that the opening is 1 cm below the surface (see Fig. 1).
Fig. 1
(ii) Measure 1 cm3 of buffer solution pH 4.0 into a clean conical flask, using a graduated pipette.
(iii) Measure 10 cm3 of the hydrogen peroxide carefully into the conical flask.
(iv) Reset the stopclock to zero.
(v) Measure 1 cm3 of the catalase solution, rapidly, into the conical flask.
(vi) Immediately place the delivery tube bung into the flask, swirl the contents and start the stopclock.
(vii) Measure the rate of oxygen production by timing the release of 10 bubbles from the end of the delivery tube. Swirl the contents continuously whilst timing the bubbles. Record your results.
(viii)Repeat the experiment for each of the different pH conditions.
You may make any modifications to these instructions that you consider
appropriate. You are reminded of the need to note these in your report.
Convert your results to the rate of oxygen production, in bubbles per minute.
Tabulate and display your results on an appropriate graph.
[15]
Comment on your observations. [10]
