Net price 56=81p
* Sodium Bicarbonate Tablets, Compound, BP
Sodium bicarbonate 300mg. Contains about 4mmol Na+/tab
Net price 50=56p
* Maalox TC (Rhone-Poulenc Rorer)
Tablets, co-maagaldrox 300/600 (magnesium hydroxide 300mg, dried aluminium hydroxide 600mg (low Na+))
Net price 100=£3.86
N.B.
Co-magoldrox is a mixture of aluminium hydroxide and magnesium hydroxide; the proportions are expressed in the form x/y where x and y are the strengths in milligrams per unit dose of magnesium hydroxide and aluminium hydroxide respectively.
Having carried out my research, I discovered that the indigestion remedies could be any of the following chemicals:
Sodium Bicarbonate or Sodium hydrogen Carbonate:
The most popular brand of medication that contains sodium carbonate is Alka-Seltzer. Alka-Seltzer has aspirin, which could be stomach irritant. This reaction should take place:
NaHCO3 + HCl ----------> NaCl + H2O + CO2
Calcium Carbonate:
Calcium carbonate is a fast acting cure. The compound is a powder made from chalk, bones and shells. Like sodium based cures these compounds are good in small doses for short-term relief. Too much calcium can damage the kidney and lead to calcium deposits.
CaCO3 + HCl ----------> CaCl + H2O + CO2
Magnesium Hydroxide:
This forms magnesium chloride (a harmless salt) and water in the stomach to calm indigestion.
Mg(OH)2 + 2HCl ----------> MgCl2 + 2H20
EQUIPMENT:
1 burette,
1 clamp stand,
4 100 ml beakers,
1 white tile,
4 conical flask,
1 top-pan balance,
mortar and pestle,
1 funnel,
1 spatula,
different brand indigestion tablets,
hydrochloric acid,
methyl orange,
pipette and pipette filler,
distilled water,
stirring rod,
measuring cylinder,
labels,
safety goggles,
lab coat.
burette - I chose to use the burette to drip the HCl accurately into the mixture of water and indigestion tablet. I chose this because it is extremely accurate and can hold up to 50ml of liquid and is accurate up to a tenth of a millilitre, for example: 10.0ml
clamp stand - To hold burette steady above the conical flask.
100ml beaker - Used to contain the mixture of distilled water and indigestion tablet.
white tile - Used for comparison to allow easier indication of when methyl orange turns "peachy".
conical flask - To contain 10cm3 of water and indigestion tablet mixture whilst it is being titrated. I chose this because it is easier to swirl the mixture, as I am adding the HCl, using a conical flask than it is using any other container.
top-pan balance - To accurately measure out the mass of ground up indigestion tablet. This can be done within one hundredth of a gram, for example : 10.00g
mortar and pestle - To grind the indigestion tablets into a fine powder. This will increase the surface area and also it will allow me to accurately measure out a similar mass for each of the indigestion tablets added, as it is now a fine powder.
filter funnel - This will be used to help fill the burette with HCl.
spatula - Used to place the finely ground indigestion tablets into the conical flasks.
different brand indigestion tablets - I decided to use different brands, as the aim of this experiment is to find the most cost effective indigestion tablets on the market. this would be the one the has the lowest cost to neutralise the acid.
hydrochloric acid - I decided to use 0,5mol of acid top represent the excess acid found in our stomachs.
methyl orange - I decided to use methyl orange (C14H14N3NaO3S), as we had previously used it in titration experiments, I had become familiar with it. I also felt that it would be better than using universal indicator solution, which undergoes several colour changes over a wide range of pH's, as there are far too many colours which may lead to debate as to when the mixture had been neutralised.
pipette and pipette filler - I decided to use the pipette and pipette filler as it was the most accurate piece of apparatus available to measure out an exact volume of mixture. It also allowed more precision over the amount of mixture added as it had a fine control.
distilled water - To mix the fine powder of indigestion tablet to allow a clearer pH reading.
stirring rod - To stir the mixture of distilled water and finely ground up indigestion tablets.
measuring cylinder - To measure accurately the amount of distilled water needed.
labels - I decided to use labels to mark the HCl and the four different mixtures of water and indigestion tablets, that way I would not mistake one mixture for another, keeping my results fair and accurate.
safety goggles - This was one of my safety aspects. As with all experiments using acid, even though this may have been relatively weak, I decided to wear goggles as acid is corrosive and could cause damage if it accidentally splashed into my eyes.
lab coat - As with all practicals it was advisable to wear a lab coat to prevent damage to my cloths.
VARIABLES:
* Input variables:
* the concentration of acid
* the starting temperature of the acid
* the starting temperature of the water and indigestion tablet mixture
* the mass of the indigestion tablet added
Throughout the entire experiment, I must ensure the certain variables are kept precisely the same. These are called controlled variables. They are necessary to make sure that the experiment is as fair and accurate as possible. Any controlled variables that are modified may lead to rouge results, which would show that something had gone wrong.
Controlled Variables:
* mass of indigestion tablet added
* volume of water
* concentration of HCl
* room temperature
The mass of indigestion tablet must be kept throughout the experiment, for each tablet. I will check that the mass of the powder is as accurate as possible. This is important because if any more or less indigestion tablet is used, it will change the amount of HCl needed to neutralise it.
The volume of water must be kept the same throughout the entire experiment. I will keep this at 10cm3 throughout the experiment.
I will keep the concentration of HCl the same throughout the experiment. As I had stated before, I will be using 0.5mol of acid to represent the acid found in our stomachs. This is important, because in order to find out which is the most cost effective at neutralising excess acid the acid being used must be as close to the acid found in our stomachs as possible.
I will keep the room temperature the same. This is important because if the room temperature was much higher or lower in one session than the other, the experiment would be greatly affected. This is because at a higher temperature collisions between the particles are more frequent. They have more energy because particles are moving a lot faster and thus they collide with more energy. In other words temperature influences the frequency of collisions between the reactants. This si why I will try to carry out all the experiments within a one hour session. Even though there will be minor fluctuations in temperature they will have minimal affect on my results.
I will be looking at how effective the indigestion tablets are at neutralising excess acid. Therefore, the only thing I will be changing is the amount of HCl added to the mixtures of water and indigestion tablets.
RISK ASSESSMENT:
All chemicals must be carefully used, and all experiments should be conducted with extreme care. Here are some points I will follow:
* safety goggles should be worn at all times
* sodium hydroxide and hydrochloric acid are corrosives so I will wash my hands thoroughly.
* place all bags under the table and well out of the way so as to not trip over it
* wear a lab coat
* no eating or drinking in the lab
FAIR TEST:
Some things I will do to make sure the experiment is fair:
* Wash the burette with a little water, followed by a small amount of acid. This is to clean it, to avoid contaminating the acid.
* I will wash all the equipment that comes into contact with either the acid or the water and indigestion tablet solution to avoid contaminating them between experiments.
* I will make sure that the bottom of the meniscus touches the line in the burette when filling it up.
* When swirling the acid and the mixture together in the conical flask, I will not put my hand around it. Instead I will hold it at the top. Otherwise, the contents may get warmed up from body heat.
* I will make sure that only the volume of acid added is the thing that changes throughout the experiment, everything else will be kept he same.
MEASUREMENTS:
I have decided that I shall each experiment I do 4 times. The first will be to give me a rough measure of how much acid to add. The remaining three will allow me to judge as to when an anomalous results crops up. It is important to do the experiment more than twice. If they were done twice one of the results may be anomalous and I wouldn't know which one, as there is not enough data to compare it with.
I will look in advance at the divisions of the burette so that I will be able to work out a percentage error at the end.
METHOD:
I will set up the apparatus as shown in the diagram at the back of the planning. I will accurately measure out 5g of finely ground indigestion tablets into clean 100ml beakers using the top-pan balance. Then I will add 100ml of distilled water. I will do this using a measuring cylinder because I want it to be as accurate as possible. The reason I am using 5g of indigestion tablets to 100ml of water is because I am using the same ratio of 0.5:10 which is what I will be using each time when I neutralise the acid. By making the mixture in bulk saves time and also allows my experiment to be fairer as it is now a standard solution. Once I have got all the different brands of indigestion tablets made into mixtures, and have mixed it using the stiring rod to make sure it has disolved, I will use the pippete to measure out 10cm3 of mixture into the conical flask before adding 2-3 drops of methyl orange and placing it on a tile for comparrison. I will then add about 1cm3 of acid at a time, shaking between additions until the indicator has turned "peachy" This first trial should give me a rough idea of how much acid to use. i will then wash all the equipment that has been contaminated and repeat the trial run for the other brands of indigestion tablets, before doing three more runs for each. I wil then work out my average.
PREDICTION:
With indigestion tablets being a consumer product, I predict that the best cure for neutralising a build up of stomach acid will be the one which has the lowest cost to successfully neutralise the dilute hydrochloric acid (HCl 0.5mol to represent the excess acid found in our stomachs). This tablet would be the one which costs less than any of the to bring the acid build up to neutral pH of 7. This is because it would make it more affordable and uses a low amount of powder at the same time.
SOURCES:
BNF (British National Formulary) 40, March 2000
Nuffield Advnced Science, Chemistry, Students Book
Oxford, Co-ordinated Science, Chemistry