Diagram-
In this entire experiment nothing should change, all the measurements should remain constant and all the type of equipment/ substances should remain constant. The only exception to this is the antacid tablet; they have to vary otherwise there wouldn’t be an experiment. If this is all followed then a fair test should happen.
Key Factors/ Variables-
The only variable in this test are the antacid tablet, of which I must change once I have a consistent set of results for the tablet before. Each tablet has different ingredients with different prices and so will have differing results:
These are the active ingredients for each tablet…
- Settlers- £3.50 for 96 tablets
0.5 g calcium carbonate (CaCO3)
- Rennies- £4.00 for 96 tablets
0.68g calcium carbonate (CaCO3)
0.08g magnesium carbonate (MgCO3)
- Bisodol- £3.50 for 100 tablets
0.522g calcium carbonate (CaCO3)
0.068g magnesium carbonate (MgCO3)
0.064g sodium hydrogencarbonate (NaHCO3)
- Boots- £2.00 for 80 tablets
0.5g calcium carbonate (CaCO3)
Prediction-
Earlier I predicted that the tablet with the most alkaline substances would take the most volume of acid to neutralise. All the above substances are alkaline and so, assuming that they must be around the same pH (they would be made the right pH so that the body could take the tablet), I can just add up how much of the alkali substances are there in each tablet and the one with the most I will predict to have the highest titration. I therefore predict Rennies to have the highest titration as it has the highest weight of alkali materials, then followed by Bisodol with the next highest weight, and then Boots and Settlers should have roughly the same amount of titration.
I can also predict how many moles of hydrochloric acid each tablet can neutralise, but it takes some calculation. In the next sets of calculations the ingredients of each mentioned tablet and the hydrochloric acid needed for its neutralisation will be seen in the formulas.
Settlers:
CaCO3 + 2HCL → CaCL2 + CO2 + H2O
Moles of the antacid tablet = Mass ÷ Relative Formula Mass (RFM)
Mass of tablets active ingredients = 0.5 g
RFM= relative atomic mass of each element added together
Ca= 40 relative atomic mass
C= 12 relative atomic mass
O3= 16 relative atomic mass x 3= 48
RFM= 40 + 12 + 48 = 100g
Moles of antacid tablet = Mass ÷ RFM = 0.5 ÷ 100 = 0.005 moles
Moles of HCl tablet should neutralise = mole of CaCO3 (which is 0.005) x however many HCl’s are needed in the experiment (which is said in the formula above) = 0.005 x 2 = 0.01 moles
I predict that 0.01 moles of HCl (hydrochloric acid) are needed to neutralise the Settlers tablet.
Rennies:
CaCO3 + MgCO3 + 4HCl → MgCl2 + CaCl2 + 2CO2 + 2H2O
Mass of active ingredients= 0.68 + 0.08 = 0.76g
RFM = Ca = 40
2C = 12 x 2 = 24
2O3 = 16 x 3 = 48 x 2 = 96
Mg = 24
RFM = 40 + 24 + 96 + 24 = 184g
Moles of antacid tablet = Mass ÷ RFM = 0.76 ÷ 184 = 0.004 (to 3 d.p) moles
Moles of HCl tablet should neutralise = mole of Rennies antacid tablet x 4 (HCl) = 0.004 x 4 = 0.016 (to 3 d.p) moles
I predict that 0.016 moles of HCl are needed to neutralise the Rennies tablet.
Bisodol:
CaCO3 + MgCO3 + NaHCO3 + 5HCl → CaCl2 + MgCl2 + NaCl + 3CO2 + 3H2O
Mass of active ingredients = 0.522 + 0.068 + 0.064 = 0.654g
RFM = Ca = 40
Mg = 24
Na = 23
3C = 12 x 3 = 36
3O3 = 16 x 3 = 48 x 3 = 144
H = 1
RFM = 40 + 24 + 23 + 36 + 144 + 1 = 268g
Moles of antacid tablet = 0.654 ÷ 268 = 0.0024 (to 4 d.p) moles
Moles of HCl tablet should neutralise = 0.0024 x 5 (HCl) = 0.0122 (to 4 d.p) moles
I predict that 0.0122 moles of HCl are needed to neutralise the Bisodol tablet.
Boots:
CaCO3 + 2HCL → CaCL2 + CO2 + H2O
Mass of active ingredients = 0.5 g
RFM= Ca= 40 relative atomic mass
C= 12 relative atomic mass
O3= 16 relative atomic mass x 3= 48
RFM= 40 + 12 + 48 = 100g
Moles of antacid tablet = 0.5 ÷ 100 = 0.005 moles
Moles of HCl tablet should neutralise = 0.005 x 2 = 0.01 moles
I predict that 0.01 moles of HCl (hydrochloric acid) are needed to neutralise the Boots tablet.
Range and Type of Measurements-
When doing my experiment I will take and record results in certain places. To get a consistent pattern I think that around 3 repetitions for each tablet will do. This will mean I’ll have to take down 6 recordings for each tablet; 3 at the start of each test and 3 at the end of each test, the difference between each start and finish gives the volume of the acid needed to neutralise the tablet.
Strategy-
When doing my method I will have to do certain actions to get reliable results and to make it a fair test. Most of these actions have already been mentioned in my method but I will clarify them anyway. The first action I must do is to only let the acid in gradually otherwise when I reach the end point I may go over it if I’m letting too much in at one time, giving me an inaccurate and useless result. I must also only use distilled water while cleaning away the chemicals from a previous experiment because that water is neutral and so won’t affect the outcome of the following experiment while normal water might giving me unreliable results, rendering the experiment unfair. I must obviously make my measurements as exact as possible, the more exact they are the fairer the test is and the better the results. Lastly when I’m at the end point but I’m not sure that it is the end point I will shake the flask for a maximum of 5 more minutes, if the liquid doesn’t start to go back to blue after that time I will assume that the test is completed.
Information from secondary sources-
“In this chapter we are concerned with the volumes of standard solutions that react exactly together; with this information various calculation can be done.
In Chapter 21, it was explained that the concentration of a solution can be expressed in terms of molarity. Alternatively the concentration of a solution may be written in terms of moles per cubic decimetre. A 0.1 M has a concentration of 0.1 moles/dm3….
A solution of known concentration or known molarity is called a standard solution. In volumetric chemistry, a series of titrations are carried out. In each titration, a solution A is added in small measured quantities, from a burette, to a fixed volume of a solution B, measured with a pipette, in the presence of an indicator. At least one of the solutions must be a standard solution. The addition of solution A is continued until the indicator just changes colour. At this stage, called the end point, the two substances are present in quantities that exactly react.
In any titration, accuracy of measurement is very important.”
Information taken from ‘Letts revise GCSE Chemistry’
Results-
Analysis-
My results told me that Rennies had the highest volume of acid used to neutralise it, the second highest was Bisodol, which was followed by Settlers and then Boots came last.
Diagrams-
From my results I realised that this was the only chart or graph that I could make that would help or be relevant. Since this tests entire aim is comparing the 4 tablets I found that the bar chart would be the best as its primary use is for easy comparison. It basically shows how Rennies has the highest volume of acid throughout the experiment, with Bisodol quite far behind it, Settlers was close to Bisodol but still third highest and Boots being really low in last place. I think that it’s interesting to note how my results (apart from Boots) gradually went up in accordance to my tests. This might have been a result of me having to do my experiments at a faster rate because of lack of time but my results still didn’t go too inaccurate, as there is only a difference of 3cm3 at the maximum in the three separate tests.
Calculations-
In my predictions I predicted the number of moles of HCl needed to neutralise each tablet. I will now found the proper amount of moles needed to neutralise each tablet from my results and some calculations.
Calculation-
Number of moles of HCl each tablet neutralises = (average) volume cm3 x the molarity of the acid (in this case I used 0.5 mole acid) ÷ 1000
Settlers-
Number of moles of HCl the Settlers tablet neutralises = 18.83cm3 x 0.5 M ÷ 1000 = 0.009415 moles. Prediction of moles before the experiment was 0.01 moles.
Rennies-
Number of moles of HCl the Rennies tablet neutralises = 26.9cm3 x 0.5 M ÷ 1000 = 0.01345 moles. Prediction of moles before the experiment was 0.016 moles.
Bisodol-
Number of moles of HCl the Bisodol tablet neutralises = 21.5cm3 x 0.5 M ÷ 1000 = 0.01075 moles. Prediction of moles before the experiment was 0.0122 moles.
Boots-
Number of moles of HCl the Boots tablet neutralises = 11.6cm3 x 0.5 M ÷ 1000 = 0.0058 moles. Prediction of moles before the experiment was 0.01 moles.
Conclusion-
I found that all but one of my results corresponds very well to my prediction. Settlers is only out by 0.0006 of a mole, Rennies is out by 0.00255 of a mole, and Bisodol is only out by 0.0015. Boots though is out by 0.0042 moles, nearly half its predicted molarity. This means that, using my calculation results, roughly 1 mole of the active ingredients in the Settlers tablet reacts with 50 moles of hydrochloric acid, 1 mole of the Rennies tablet reacts with around 37 moles of HCl, 1 mole of the Bisodol tablet reacts with around 46 moles of HCl and 1 mole of the Boots tablet will react with roughly 86 moles of HCl.
From all these results you can see that nearly my entire prediction is proved right. Rennies does take the highest volume of acid, then Bisodol does follow, Settlers does come third and then the only thing wrong with my prediction is that Boots doesn’t tie with Settlers, it falls quite far below it. As I’ve said already all but the Boots tablet followed my predicted molarity. I therefore conclude that Rennies are the best antacid tablet to buy out of these four even though it’s the most expensive, its quality is worth the price.
Evaluation-
I found that the experiment was very time- consuming and had to be very accurate to get reliable results. I think though that my results were quite accurate as they managed to fit into the calculated, exact predictions very well except for the Boots antacid tablet.
This experiment was suitable for my aim but time is needed to get useful results. It is though only needed for proof of any calculations because any molarity, concentration or volume measurements can be figured out straight away with the right amount of information and calculations. Other than that though the actual experiment itself was very suitable as it had all the right equipment to test the antacid tablets (like the use of acid to neutralise the tablets because they’re alkali and the use of an indicator so that it’s easy to read when it changes from acid to alkali and adding water so that an indicator can be used and other things like that). To improve the reliability of the results I would change the equipment to something more accurate because accuracy is the most important thing in this experiment. This equipment might include an electronic stirrer that stirs the liquid up at a constant rate, or maybe a pH tester so that I could make sure that the distilled water is neutral and definitely won’t affect my next test, just equipment like that would make my experiment that bit more accurate.
I believe that my results were also reliable (apart from the Boots tablet) as I did the experiment properly following the method and fair test rules. It didn’t cut corners to quicken the tests or make up the results; everything was applied. The reason that my Boots experiment went wrong is because I was rushed for time and so had to hurry in completing all 3 of the tests and that obviously must have made the experiment go wrong. It was either this or the calcium carbonate in the tablet was affected in some way by the other inactive ingredients or was wrong to begin with. I found that there were enough results in the end to read from because I managed to make a useful graph, confirming my prediction and see the patterns and trends of the tablets.
If I was to do this experiment again there are a number of thing that I’d change. I’ve already said that I would add more equipment into the experiment, but I would also change the amount of water (10ml of water) or tablets used (only 1 tablet was used). Changing the amounts of each item to larger would give better accuracy but would also be more time-consuming or changing it to smaller amounts would save time but also be less accurate. At the moment the amounts were around the middle. Any further works would include repeating the experiment again to confirm my conclusion or to try and use the chemicals in the tablets as separate materials in their own experiments and see whether they work in the same way against the same acid as in this experiment. If it did that it would also confirm what I found out in my experiment. The main thing that I would like to do as further work though is to check whether the Boots tablet was an anomalous result or if it’s just a useless tablet by using a series of different tests.
