To determine the effectiveness of an indigestion tablet at neutralising acid.

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Chemistry Practice Plan March 2003

To determine the effectiveness of an indigestion tablet at neutralising acid.

The stomach produces Hydrochloric acid, which provides a medium for the digestion of protein by the enzyme protease.  An excess of acid can lead to indigestion, many tablets are on the market to help neutralise this excess acid, but all have different ingredients.

 

I am to find out which commercially available indigestion tablet is most effective;

 

The brands in bold are the six that I have chosen to investigate

Equipment

As there are six different brands available, the equipment list below may need to be multiplied by 5.

250ml beaker

Pestle and Mortar            

Magnetic stirrer

Burette

2x Stand, Clamp and Boss

Distilled water

pH 7 buffer solution

Pipette

Top-pan balance

PH probe

Laptop with appropriate software     


Method

There are many ways of doing this experiment, but titrating 1 molar acid onto the tablet, is by far the simplest, as well as being effective and time efficient.  1 molar acid is usually available; however, it can simply be made by diluting more concentrated acids with distilled water.  The burette should be thourgherly cleaned out, using distilled water.  Then the acid ("titrant") should carefully be filled into the burette using a funnel.  It should be filled to the zero level, pipetting (at eye level) if necessary to reach the value accurately. Check for bubbles in the valve of the burette, and if necessary refill after releasing the bubbles.

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The tablets should be crushed using the pestle and mortar, so they resemble a fine powder. Measure out 100ml of distilled water into a measuring cylinder and then add to the first tablet in the beaker.  

Set up the apparatus as shown, and calibrate the pH probe using the buffer solution.

Turn on the magnetic stirrer to an appropriate speed.  Most tablets will dissolve in this time, however, if they don’t dissolve, continue with the experiment, as the neutralisation reaction will still occur once the acid is adding, however it may take longer to react.

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