Planning Experimental Procedures

Our aim of this experiment is to find out which antacid tablet works the best. In this project we were trying to find out how the speed at which an ordinary indigestion tablet will dissolve when it comes into contact with Hydrochloric Acid, which is more commonly found in the stomach. We already know that the formula for the reaction that takes place is:

2HCl + CaCo3 = CaCl2 + CO2 + H2O

Acid indigestion is when you eat a lot of acidic food and drinks, so your stomach becomes acidic and causes pain. Antacid tablets are tablet, which are strong alkalis, and so when you swallow them, the tablets neutralise the acid.

Stomachs contain hydrochloric acid. It breaks down the chemicals in food. If too much is eaten some of the acid washes up into the oesophagus causing pain due to the acid corroding the lining. This is commonly known as indigestion. Indigestion tablets are bases (the opposite of acids) and so when the two substances come into contact they neutralize each other. This stops the lining of the oesophagus from being damaged and so the pain subsides.

Word and Formula Equations for the antacid tablet Settlers Superdrug and Rennie Rap-eze (fruit flavour).

Calcium carbonate (s) + Hydrochloric acid (aq) –> Calcium Chloride (aq) + Carbon Dioxide (g) + Water (l)

Ca CO3(s) + 2 HCl (aq) –> Ca Cl2 (aq) + CO2 (g) + H2O (l)

Word and Formula Equations for the Rennie (pepper mint flavour) antacid tablet.

Calcium carbonate (s) + Hydrochloric acid (aq) –> Calcium Chloride (aq) + Carbon Dioxide (g) + Water (l)

Ca CO3(s) + 2 HCl (aq) –> Ca Cl2 (aq) + CO2 (g) + H2O (l)

Magnesium carbonate (s) + Hydrochloric acid (aq) –> Magnesium Chloride (aq) + Carbon Dioxide (g) + Water (l)

Mg CO3(s) + 2 HCl (aq) –> Mg Cl2 (aq) + CO2 (g) + H2O (l)

Word and Formula Equations for the Boots and Bisodol antacid tablet.

Calcium carbonate (s) + Hydrochloric acid (aq) –> Calcium Chloride (aq) + Carbon Dioxide (g) + Water (l)

Ca CO3(s) + 2 HCl (aq) –> Ca Cl2 (aq) + CO2 (g) + H2O (l)

Magnesium carbonate (s) + Hydrochloric acid (aq) –> Magnesium Chloride (aq) + Carbon Dioxide (g) + Water (l)

Mg CO3(s) + 2 HCl (aq) –> Mg Cl2 (aq) + CO2 (g) + H2O (l)

Sodium bicarbonate (s) + Hydrochloric acid (aq) –> Sodium chloride (aq) + Carbon Dioxide (g) + Water (l)

NaHCO3 (sol)+ 1HCl (aq )–> 1Na Cl (aq)+ H2O (aq) + CO2 (gas)

Initial Calculations.

For all these calculations I shall be using 1 Molar of hydrochloric acid.

Moles of antacid acid = mass / relative formula mass

Number of moles of acid needed to neutralise antacid tablet:

= 2 x number of moles of the antacid chemical.

Predicted volume of acid needed to neutralise the antacid:

= Moles of acid

———————– = predicted volume in dm3

Concentration of acid

To change dm3 into cm3 you times it by 100.

Calculations for Settlers, Superdrug and Rennie rap- eze .

Moles of antacid= 500 mg (0.5g) divided by 100 (RFM) = 0.005 moles

Number of moles= 2 x 0.005 moles = 0.010 moles of acid needed to neutralise the antacid tablet.

Predicted volume of acid = 0.01 moles divided by 1= 0.01 dm cubed

0.01 x 1000 = 10 cm cubed to neutralise the antacid.

Calculations for Rennie (pepper mint flavour) antacid tablet.

Note: This tablet is different to the ones above it has an extra carbonate ingredient so it will be different.

Number of moles in each chemical in Rennie (pepper mint flavour):

For Calcium carbonate.

Moles of antacid = 680 mg (0.68g) divided by 100 (RFM) = 0.0068 moles

Number of moles of acid = 2 x (0.0068 moles) = 0.0136 moles of acid.

Predicted volume of acid =0.0136 moles divided by 1= 0.0136 m cubed

So you shall times this by 1000 to get it in cm cubed so it shall equal = 13.6 cm cubed to neutralise the antacid.

For Magnesium carbonate.

Number of moles = 80 mg (0.08g) divided by 84 (RFM) = 0.001 moles

Moles of the acid= 2 x 0.001 moles = 0.002moles of acid needed to neutralise the antacid tablet.

Predicted volume of acid needed to neutralise the antacid: = 0.002 moles divided by 1= 0.002dm cubed

So you shall times this by 1000 to get it in cm cubed so it shall equal = 0.2 cm cubed to neutralise the antacid.

Predicted volume= 0.2 cm cubed + 13.6 cm cubed = 13.8 cm cubed of acid needed to neutralise the tablet

Calculations for Boots antacid tablet.

Note: This tablet is different to the ones above but it has the same ingredients as boots antacid tablet.

For Calcium carbonate.

Number of moles of antacid= 200 mg (0.2g) divided by 100 (RFM) = 0.002 moles

Number of moles of acid = 2 x 0.002 moles = 0.004 moles of acid needed to neutralise the antacid tablet.

Predicted volume of acid needed to neutralise the antacid= 0.004 moles / 1= this will equal 0.004 dm cubed

So you shall times this by 1000 to get it in cm cubed so it shall equal = 4 cm cubed of HCl to neutralise the antacid.

For Magnesium carbonate.

Number of moles = 600 mg (0.06g) divided by 84 (RFM) = 0.0007 moles

Number of moles of acid = 2 x 0.0007 moles = 0.0014 moles of acid

Predicted volume of acid needed to neutralise the antacid:

= 0.0014 moles divided by 1= this will equal 0.0014dm cubed

So you shall times this by 1000 to get it in cm cubed = 1.4 cm cubed to neutralise the antacid.

For Sodium Bicarbonate.

This number will be two because the reaction is:

NaHCO3 (sol)+ 1HCl (aq )–> 1Na Cl (aq)+ H2O (aq) + CO2 (gas)

There is a 1 :1 reaction there are 1 hydrochloric acids to react with 1 magnesium carbonate.

= 1 x 0.0007 moles = 0.0007 moles of acid needed to neutralise the antacid tablet.

Predicted volume of acid = 0.0007 moles divided by 1= this will equal 0.0007 dm cubed

So you shall times this by 1000 to get it in cm cubed 0.7 cm cubed to neutralise the antacid.

The amount of acid to neutralise the antacid shall equal the amount it took to neutralise the calcium carbonate plus the amount it took to neutralise the magnesium carbonate and sodium bicarbonate:

4 + 1.4 + 0.7 = 6.1 cm cubed of acid needed to neutralise the tablet.

Calculations for Bisodol antacid tablet.

Note: This tablet is different to the ones above it has 2 extra carbonate ingredients so it will be different.

Number of moles in each chemical in Boots antacid tablet:

For Calcium carbonate.

Number of moles = 522 mg (0.522g) divided by 100 (RFM) = 0.00522 moles

Number of moles of acid = 2 x 0.00522 moles = 0.01044 moles of acid

Predicted volume of acid needed to neutralise the antacid:

= 0.01044 moles divided by 1= this will equal 0.01044 dm cubed

So you shall times this by 1000 to get it in cm cubed so it shall equal =10.4 4 cm cubed of HCl to neutralise the antacid.

For Magnesium carbonate.

Number of moles = 68 mg (0.068g) divided by 84 (RFM) = 0.00081 moles

Number of moles of acid = 2 x .00081 moles = 0.0016 moles of acid

Predicted volume of acid = 0.0016 moles divided by 1= this will equal 0.0016dm cubed

So you shall times this by 1000 to get it in cm cubed so it shall equal = 1.6 cm cubed to neutralise the antacid.

For Sodium Bicarbonate.

Number of moles = 64 mg (0.064g) divided by 84 (RFM) = 0.00076 moles

Number of moles of acid=1 x 0.00076 moles = 0.00076 moles of acid

This number will be one because the reaction is:

NaHCO3 (sol)+ 1HCl (aq )–> 1Na Cl (aq)+ H2O (aq) + CO2 (gas)

There is a 1: 1 reaction there are 1 hydrochloric acids to react with 1 sodium bicarbonate.

Predicted volume of acid =0.00076 moles / 1= this will equal 0.00076 dm cubed

So you shall times this by 1000 to get it in cm cubed so it shall equal = 0.76 cm cubed to neutralise the antacid.

The amount of acid to neutralise the antacid =10.44 + 1.6 + 0.76 = 12.8 cm cubed of acid needed to neutralise the tablet.

We needed a list of apparatus to do this experiment. We needed a clamp, a boss, a burette, an indicator, a beaker, goggles, a white tile, a funnel, a conical flask, an indigestion tablet, distilled water, a measuring cylinder, a crusher (grinder), and finally hydrochloric acid. We set it up like this.

In our preliminary work we used the Superdrug indigestion tablet for our experiment. We first put the indigestion tablet into the crusher and crushed it, we did not have to crush it was optional. Once it was crushed we put it in a conical flask with 100ml of distilled water and a choice of indicator, we used five drops of universal indicator, which made the solution purple, for our preliminary work. We than took a clamp and attached a boss to it, which would than be attached to a 50cm-cubed burette. Next, we took 1m-hydrochloric acid and put it in a beaker instead of straight into the burette, for safety. To be a bit safer we put the clamp, with the burette, on to a stool so it was at eye-level and than put a funnel on the top of the burette, filling it up with hydrochloric acid. We put the clamp back on to the table, with a whit tile underneath and the conical flask. We had to make sure we were comfortably sitting down, although in most chemistry experiments we are expected to stand and do it. Than we let the hydrochloric acid slowly drip into the conical flask, whilst stirring it at the same time until the solution turned yellow, acidic.

We did the same experiment three times with the same tablet and recorded our results in a table.

Experiment 1

Experiment 2

Experiment 3

Average

Start

0cm-cubed

0 cm-cubed

0 cm-cubed

0cm-cubed

Finish

7.2cm-cubed

7.5cm-cubed

9.35cm-cubed

8.02cm-cubed

Titration

7.2cm-cubed

7.5cm-cubed

9.35cm-cubed

8.02cm-cubed

So in the first experiment it took 7.2cm-cubed of 1m-hydrochloric acid to neutralise the solution, in the second it took 7.5cm-cubed, and in the final experiment it took 9.35cm-cubed of hydrochloric acid.

To make sure that the experiment was perfectly safe we had to wear safety goggles, so that hydrochloric acid would not splash in our eyes, whilst stirring the solution. We will make sure that all bags and stools are neatly placed under the tables. We always used the funnel when pouring the hydrochloric acid in the burette and made sure that it was at eye level.

To ensure a fair test I will keep all the variables the same apart from the one I am testing. This variable is the titration of hydrochloric acid. I am finding out how much hydrochloric acid it takes to neutralise an indigestion tablet.

The Variables are: the temperature of water, volume of acid, type of acid, concentration of acid, mass of indigestion tablet, and the size/shape of indigestion tablet.

I could make the experiment a lot more accurate and fair if we had done it by using data logging, with a magnetic stirrer.

After doing the preliminary experiment we changed the indicator, which we used because universal indicator did not show accurate results, clearly. So now, instead, we use Bromophenol blue indicator because we were told it was the best indicator, giving clear results.

After we had finished the preliminary work, we started the secondary experiments.

We now have to get five different indigestion tablets and do the experiment to check which one works the best, repeating the same experiment three times. The five indigestion tablets we had were, Superdrug, Bisodol, Boots, Rennies, and Settlers.

These are the predictions that I made for how much hydrochloric acid would be used to neutralise each tablet.

TABLET

AVERAGE TITRATION

Superdrug

10cm-cubed

Bisodol

12.9cm-cubed

Boots

6.1cm-cubed

Rennies

15.5cm-cubed

Settlers

10cm-cubed

To work out these predictions I have to know the relative formula mass of the active ingredient, which was calcium carbonate, magnesium carbonate, or sodium bicarbonate. I also had to know the mass of the antacid tablet and the moles of the hydrochloric acid.

Once I find out the relative formula mass of the active ingredient, I divide it with the mass of the active ingredient. If the ingredient was sodium bicarbonate you leave the formula to the next stage but if it were calcium carbonate or magnesium carbonate I would multiply it by two. The next stage is to divide the answer with the concentration of the hydrochloric acid, mine was one molar and so we did not have to go through this final stage. The answer that you get will be in dm-cubed, to convert it to cm-cubed we simply multiply it by one thousand.

I will show you how I found out how much hydrochloric acid it took to neutralise the superdrug tablet, as an example.

The RFM for calcium carbonate=40+12+16+16+16=100

0.5(Mass)/100(RFM)=0.005

0.005*2=0.01dm-cubed

=10cm-cubed

So my prediction is that Rennies indigestion tablet works the best, than Bisodol, superdrug and settlers are equally good, and boots indigestion tablets work the worst out of the five.

There will be a reaction between the acid and the indigestion tablet because indigestion tablets are designed to neutralise stomach acid. The hydrochloric acid that I am using is very similar to the acid that is in the stomach.

Carbonates all react with acids to give off carbon dioxide,

With an acid to produce a salt + water + carbon dioxide.

The formula for the reaction of Calcium Carbonate and Magnesium Carbonate are the similar. This is shown below.

Calcium + hydrochloric = calcium + water + carbon this writing

Carbonate acid chloride dioxide

CaCO3 + 2HCl = CaCl2 + H2O + CO2

Hydrochloric Acid + Magnesium = Magnesium + water + carbon

Carbonate chloride dioxide

Sodium bicarbonate is also know as sodium hydro carbonate

Sodium hydro carbonate is used in baking. The carbon dioxide gas it gives off when heated makes dough rise. It is also used as an antacid to relieve indigestion

Therefore, as the sodium bicarbonate is warmed by being in hot acid it could break down into sodium carbonate, water and carbon dioxide. This carbon dioxide will add to the volume of gas being produced.

2NaHCO3 = Na2CO3 + H2O + CO2

This sodium carbonate would then react with the acid to form sodium chloride, water and carbon dioxide.

2HCl + Na2CO3 � 2NaCl + H2O + CO2

Alternatively the sodium bicarbonate could react directly with the acid

HCl + NaHCO3 = NaCl + H2O + CO3

The other active ingredient is magnesium Trisilicate. This does not contain any carbon atoms so will not produce carbon dioxide when it reacts with the acid.

Obtaining Evidence

When we were doing the experiment, we had to make sure all our measurements were correct so that it did not affect our results.

When we put the indicator in, we had to make sure that we put exactly the same amount of drops in (by using a dripper), which were seven drops.

When we added the water to the antacid tablet we made sure that we put exactly 100ml of the distilled water in. this was done by using the measuring cylinder, even though it really would not have affected the results if we put a bit too much or a bit too less water in.

We also had to note down how much hydrochloric acid we put in at the beginning at the end. The dripping did not have to start at 0cm-cubed, as long as we noted down the starting and ending results of how much hydrochloric acid we put in, so that we could work out the titration.

When we first put the antacid and distilled water into the conical flask, we saw that the Bromophenol blue indicator turned purple, to show that the solution was a strong alkali. As we dripped the hydrochloric acid, you could see that where the acid had dropped into the solution that area turned yellow, but as we stirred it the solution went back to purple again. As we got down to 8cm-cubed of hydrochloric acid used, the whole solution turned yellow and it took some time for it to change back to an alkali solution again.

When we reached the final result (for the Superdrug indigestion tablet it was somewhere near 9.5cm-cubed of 1m-hydrochloric acid) the solution would stay yellow, acidic, and would not be able to turn back to an alkali, no matter how long you would stir it for.

When we was doing the experiment, and was adding the 1m-hydrochloric acid to the solution, you could see that on some of the tablets not all of it had dissolved properly, where as some the whole tablet had completely dissolved. This would affect the results, which we had gathered.

Analysing Evidence And Drawing Conclusions

We had done the experiment three times for each tablet. There were five tablets and so we had done fifteen experiments.

By looking at the following results you will see that rennies worked the best, as it took an average of 14.7cm-cubed of hydrochloric acid to neutralise it. Boots were the worst because it only took 9.3cm-cubed of hydrochloric acid to neutralise it.

TABLET

AV. START

AV. FINISH

AV. TITRATION

Superdrug

0cm-cubed

9.53cm-cubed

9.53cm-cubed

Bisodol

0cm-cubed

12.83cm-cubed

12.83cm-cubed

Boots

0cm-cubed

9.33cm-cubed

9.33cm-cubed

Rennies

0cm-cubed

14.73cm-cubed

14.73cm-cubed

Settlers

0cm-cubed

11.3cm-cubed

11.3cm-cubed

Superdrug was not much better than the Boots antacid tablet, according to the results the Superdrug tablet only took 0.2cm-cubed more hydrochloric acid than the Boots. Bisodol was the second best, working tablet and than it was the Settlers indigestion tablet.

These were the results, which we gathered, in our first experiment.

TABLET

START

FINISH

TITRATION

Superdrug

0cm-cubed

9.6cm-cubed

9.6cm-cubed

Bisodol

0cm-cubed

12.5cm-cubed

12.5cm-cubed

Boots

0cm-cubed

13.3cm-cubed

13.3cm-cubed

Rennies

0cm-cubed

15.2cm-cubed

15.2cm-cubed

Settlers

0cm-cubed

12.5cm-cubed

12.5cm-cubed

As you can see the results which we had gathered for the Boots indigestion tablet is a lot higher than the average amount of Hydrochloric acid a boots indigestion tablet can take until it becomes neutralised.

These were the result which we had gathered for the second experiment.

TABLET

START

FINISH

TITRATION

Superdrug

0cm-cubed

10.0cm-cubed

10.0cm-cubed

Bisodol

0cm-cubed

12.7cm-cubed

12.7cm-cubed

Boots

0cm-cubed

6.7cm-cubed

6.7cm-cubed

Rennies

0cm-cubed

14.7cm-cubed

14.7cm-cubed

Settlers

0cm-cubed

11.2cm-cubed

11.2cm-cubed

The results that I collected from this lesson looked a lot more like the results which I had predicted, this could be because there was more accuracy but you can tell by comparing the results from this lesson and my predicted results, that they are very similar.

These were the results we gathered from the third and final experiment.

TABLET

START

FINISH

TITRATION

Superdrug

0cm-cubed

8.9cm-cubed

8.9cm-cubed

Bisodol

0cm-cubed

13.2cm-cubed

13.2cm-cubed

Boots

0cm-cubed

7.8cm-cubed

7.8cm-cubed

Rennies

0cm-cubed

14.3cm-cubed

14.3cm-cubed

Settlers

0cm-cubed

10.2cm-cubed

10.2cm-cubed

These results were completely different to those that I had got during the first experiment we done but I do not see any unusual results.

In this graph I decided to compare the two indigestion tablets, superdrug and boots. I chose these two because they had pretty similar results, as you can see from looking at the graph.

This is a simple line graph comparing the two indigestion tablets. You can see that the superdrug results were similar in all three experiments, unlike the boots results, where the first one maybe an anomaly.

This is a graph that I plotted for the first experiment we did. You can see clearly in each graph, for the first second and third experiment that Rennies indigestion tablet has always had the highest result. All the other results have changed.

These three graphs show clearly the results, which we collected from all three experiments. The good thing about them is that you can easily compare the results of each experiment. Like, for example, you can see easily that the Rennies indigestion tablet has been the beest and given the best results in all three experiments.

You can also see from the graphs that the boots indigestion tablet has given a pattern of low results, apart from in the first experiment, which may be an anomalous result.

This graph gives you the same data as above but all in one graph rather than three.

The purple bar displays results from the first experiment, the maroon coloured bar displays the amount of hydrochloric acid it took to neutralise the tablets in the second experiment. The yellow bar shows us the information we collected form the third and final experiment.

You can see clearly that all of the Rennies result are very high

from looking at all of these graphs I can easily conclude that the best tablets you can by is Rennies. This is clearly shown in the graphs and the results.

It takes a lot more hydrochloric acid to neutralise the Rennies tablets than any other indigestion tablet. This does explain why the Rennies tablets are the most expensive out of the five.

Rennies cost �4.00 for 96 tablets, Bisodol costs �3.50 for 100 tablets, Superdrug costs �3.00 for 96 tablets, Boots cost �2.00 for 80 tablets and finally settlers cost �3.00 for 80 tablets.

There is a pattern with the costs of the tablets. The best ones cost the most, Rennies, and the worst one is the cheapest, Boots.

Rennies are clearly the best working antacid tablets, than it is bisodol, settlers, superdrug, and the worst are Boots. This is shown in the graph below.

This graph shows the average titration of hydrochloric acid it took to neutralise each tablet. To support my conclusion you can clearly see that the rennies bar is the highest and so this shows that the rennies tablet can take a higher amount of hydrochloric acid than any othe indigestion tablet before it becomes neutralised.

I said at the beginning in the planning my predictions. My prediction was that Rennies was the best tablet than bisodol, than settlers, than superdrug and boots were the worst. I was correct but through this final graph we will see how close my prediction was.

This graph shows that my predictions were accurate. The purple bar is the average titration and the maroon coloured bar is my predictions. By looking at them you can see that I was accurate apart from the prediction for boots. This could be because of the anomalous result, which I pointed out earlier.

All of the above the calculations tables of results and graphs show that Rennie (pepper mint flavour) was definitely the most effective. As I predicted in the above prediction I thought Rennie would be the best and also I predicted that it would be close between Rennie and Bisodol, which it was very much so. These results are very close to my initial calculations so therefore this is suggesting that my test was fair and was conducted to an extent of accuracy to give me such results. As you can see in my average table I found that I had got exactly what I predicted for the Rennie tablet, which again shows the accuracy of my test.

Evaluating Evidence

The procedure was relatively safe, fair and accurate but by looking at some of the results it looks as though we could have improved it, for example the anomalous result for the boots tablet.

When we were performing the experiment we had made some faults, which might have affected the results. When we crushed the tablets, not all the powder had gone into the conical flask because it had either been blown out of the bowl or it was stuck in it and will not come of. So if not the entire tablet had gone in the conical flask, than this could affect our results because you may get a lower result than expected.

Another aspect, which may have affected the results, was that I noticed we often spilt some of the solution whilst stirring it. This than creates the same problem because some of the powder of the tablet has been spilt out and therefore cannot neutralise the acid.

A mistake we often made was forgetting to record the results after the experiment and so a lot of the time we had to guess what it was. This might have been what happened with the anomalous result.

If we did the experiment perfectly right we should have got the results that I had predicted but we did not and so things must have gone wrong.

The temperature of the water may have been different whilst recording the results for one tablet to another. If the water was warmer than I think that the results would be higher than expected and if it was colder than the results should be below average.

We may have used a different concentration of hydrochloric acid form one time to another and this definitely changes your results. We did make this mistake once but we solved it. We accidentally used 0.5m-hydrochloric acid instead of 1m-hydrochloric acid so we simply solve the problem by dividing our result in two, although this result would not be very accurate.

All these problems could have been solved if we just used better and more accurate equipment. We were shown the same experiment but by using more accurate equipment. A magnetic stirrer was used and also a tablet was put in to automatically tell us the ph of the solution, this was all wired up to a computer, where it displayed the information on the screen, by using data logging.

I think that if we had the magnetic stirrer and the data logging system, than our results would be a lot more accurate and may match my predictions made.

The case could also be solved just by simply doing the same experiment a few more times, to get more results because with only three results you do not know if you have an anomalous result unless one result is completely different to the other two.

The evidence is not strong enough to support a firm conclusion because we have just not got enough but I can tell you that Rennies is the best indigestion tablet.

I found throughout the experiment and through my results that my experiment must have been conducted well and to such an extent of fairness to get results as close as the predictions. Although this may be the case but it can always be able to be improved.

The accuracy I feel was sufficient because I have spent time on taking down results and observating things when appropriate. This suggests this will be very hard to improve this an only way is to spend even more time observating the results but this may effect the experiment.

As you can see in the above results table there are not many anomalous results again therefore suggesting that my experiment was a success and very fair.

I could have improved this test by using a pH probe and a computer program to see when it has exactly reached the pH 1 which would make the test very fair. Also I could have repeated it with a wider range of tablets, which may have gave us a wider range in results to compare.