Investigation into the efficiency of various indigestion tablets Essay Example

in which I dissolve the tablet must remain the same, so that all solutions are of the same concentration.

I cannot simply dissolve one tablet, as the masses of the different tablets vary. Instead, I will use a pestle and mortar to grind the tablet and weigh the set amount of powder for each of the tablets. The indicator that I use will also have to stay constant, as well as the amount of indicator added to the solution. There is only one variable that I have to vary. That is of course the factor that I want to investigate, which is the powders with different concentrations of active ingredients.

I will only vary the powder that I use, all the other factors will have to remain constant. Initial plan firstly, I will crush up one indigestion tablet using a pestle and mortar. I will weigh out 1g of that, on a sensitive pair of scales. I will have to do this carefully, as the amount I dissolve into the water will affect the amount of HCl needed to neutralize it.

I will dissolve that 1g. of powder into 25 cm3 of deionized water. Tap water will have impurities and will contain other chemicals which will affect the reactions that are to take place. I will add three drops of phenolphthalein, which will cause a color change when the solution becomes pH neutral.

I will fill a burette with 0.1M HCl. I will put the indigestion tablet solution in the conical flask, as that is the solution that I want to know something about. I will keep adding HCl to the solution until the solution turns from bright pink

to light pink, as that would mean that the solution is neutral.

Problems and Mistakes

When trying out this method, I experienced quite a few problems.

Firstly, it seemed like the phenolphthalein didn't suit my experiment. There was a weak base to a strong acid reaction taking place and therefore phenolphthalein did not work. Methyl orange covers the neutralization point and is, therefore, more useful. Methyl orange is yellow if pH is above 4 and red at pH below 4. Phenolphthalein would be more useful if we had a strong base and a weak acid, as it is colorless below pH 8 and red above pH 9.6. In my final method, I will therefore use methyl orange instead of phenolphthalein. Secondly, I noticed that 1g. of powder was simply too much. Even after adding a full burette (50 cm3 ) of HCl, the solution would not change color.

I decided that if I reduced the amount of powder added to the water, I would dilute the solution, thus making it take less HCl to neutralize it. If I'd reduce the amount of powder added to the water with all samples and all tablets, the results would remain the same. Also, after weighing the powder and putting it into the water, some powder would remain in the plastic cup. Even though this is only a very small amount, the experiment would be more precise if I could get this into the water. To do this, I will measure another 10 cm3 - using an accurate pipette - which I will use to rinse the plastic cup. The water will "pick up" all bits of powder left in the plastic cup.

I

must add 10 cm3 on top of the 25 cm3 in every sample, to make this a fair experiment.