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Chemistry
Sensors:
Loggers:
pH
Any EASYSENSE
Logging time: 1 minute
Teacher’s notes
06 Comparing the effectiveness of antacids
Read
A popular cure for acid indigestion is to take an antacid, these stop acid indigestion by neutralising the
acid in the stomach with a mild alkaline substance. Some of the more modern antacids work by stopping
the stomach from producing the acid in the first place, often you can work out the difference by
reading the description on the box. Those brands offering “immediate relief” are more likely to be
based on the alkali, the brands offering “up to 12 hours relief” will be more likely to stop the acid
being produced.
There are many brands of antacids available. In this investigation different brands of antacids are
tested to see which one, if any, is the most effective and possibly what the best value to buy is.
The investigation is useful in that it provides an everyday application of some simple chemistry, even if
the students are not familiar with indigestion they will have seen the advertisements for such cures
and be familiar with the idea.
Apparatus
1.
An EASYSENSE logger.
2. A Smart Q pH sensor.
3. Large beaker and wash bottle of distilled water (to rinse pH electrode after each use).
4. Stirrer – a simple glass rod or a magnetic stirrer.
5. 4 beakers of different types of antacid labelled A, B, C and D. E.g. 20 cm3 of antacid solution
made by dissolving 5 g of antacid in 50 cm3 of distilled water. As an alternative use powdered
antacid or a crushed tablet to produce a much more dramatic reaction.
Note: Solutions should all be the same temperature.
6. 4 x 100 ml beakers containing the same volume (20 cm3) and concentration of acid (0.1 mol dm-3
hydrochloric acid) or cola
Set up of the software and logger
Use the setup file 06 Antacids.
To set the logger and software manually use the details in the table,
Recording method
Total recording time
Display
Graph
1 minute
Overlay mode
L2 Chemistry
T06 - 1(V2)
The intersample time is not particularly important, but don’t be tempted to go too short, the frothing
and fizzing will create jumps in pH which can give a jagged recording. Using a longer intersample time
effectively smoothes the data. The setup file uses the default intersample time for the 1 minute
recording time.
Notes
The frothing and fizzing should be mentioned, it can catch some individuals by surprise. Students may
not immediately recognize that the froth has potentially harmful effects, their experience will have
suggested to them that foams and froths are fun.
The extension suggests using the work to calculate the cost of an antacid to cure indigestion. This is a
good exercise in using fact to find value for money and to move the science out of the test tube and
into life. If you intend to use commercial anti indigestion products do read the labels carefully, many
of the modern products are chemical inhibitors of nerve pathways in the stomach and stop the
stomach from producing acid rather than neutralising it. A simple test is to look for a mention of one
tablet lasts 12 hours. Usually acid neutralisers have short action period due to digestive transit times.
L2 Chemistry
T06 - 2(V2)