acids can be cancelled out by other substances. Substances that cancel out acids
are called bases - if a base is soluble in water it is called alkali. When a base
reacts with an acid it cancels out the effect of the acid. Bases such as Magnesium
Oxide are used to give fast relief from the effect of acid indigestion. Acid
indigestion is caused by too much Hydrochloric acid in your stomache. The bases
in the medicine cancel out the effect of the extra or excess acid in your stomache.
The reaction between an acid and a base is called NEAUTRALISATION.
Acid contains H+ ions, the stronger the acid the higher the concentration of
H+ ions. Alkalis also have similarities in their formula. They contain Oxygen (O)
and Hydrogen (H) atoms joined together as OH- ions. This combination of atoms
in a base is called a Hydroxide group. Alkalis such as Sodium Hydroxide and
Potassium Hydroxide contain this group. Alkalis also dissolve in water and break
up into positive and negative ions. When an alkali dissolves in water, the
resulting solution contains the negatively charged Hydroxide ions, OH-.
Alkalis contain OH- ions, the stronger the alkali, the higher the concentration of
OH- ions.
H+ions + OH- ions ---> H2O
The amount of H+ is the same as the amount of OH- and this is the
neautralisation point. Since OH- is a stronger alkali you have to add double the
amount of acid to ensure it is neautralised.
example:
H+ OH-
0.1m 0.2m
20ml 40ml
(neautralised)
Acids react with alkalis and the reaction is called neautralisation. On
neautralisation, the Hydrogen and Hydroxide ions react together to produce
water molecules.
Antacids are tablets which help relief pain from the stomache. When too much
HCl (Hydrochloric acid) is formed in your stomache, it causes the stomache to
ache. The antacids contain bases which neautralise the excess acid. The active
ingredient in any antacid are bases:
acid + base ---> a salt + water
Alkali has to be added to neautralise the acid in tablet form which would add the
addition of OH- ions (alkali). The tablet containing OH- ions then reacts with H+
ions to become H2O. Our tablet will work by neautralising the acid which attacks
the stomache lining. The equations for neautralisation is as follows:
H+ + OH- ---> H2O
Hydrogen + Hydroxide ---> Water
Our equation is:
CaCO3 + 2HCl ---> CaCl2 + H2O + CO2
Calcium Carbonate + Hydrochloric acid ---> Calcium Chloride + Water
+ Carbon Dioxide
In my opinion, the best tablet out of Rennies, Tesco's and Tumms will be Rennie
because it contains the most CaCO3 and also MgCO3:
CaCO3 MgCO3
Rennie 680mg 80mg
Tescos 500mg -------
Tumms 500mg -------
* ( ------- = no result )
From this table, you can see that Rennie will be the most effective tablet because
it contains MgCO3 and the most CaCO3 and the more CaCO3 there is, the quicker
the neautralisation will take place. I think Rennie will also be the most effective
because it will neautralise the most acid.
Results:
Rennie:
1 2 3 4 5
Initial 4.1 3.8 4.3 3.6 2.4
Final 21.1 20.9 25.7 18.9 15.25
Volume 17.0 17.10 21.4 22.5 17.65
Tesco:
1 2 3 4 5
Initial 2.4 3.8 4.9 3.2 6.1
Final 10.07 12.9 12.6 10.82 14.8
Volume 7.67 9.1 7.70 7.62 8.7
Tumms:
1 2 3 4 5
Initial 3.30 4.1 3.8 2.4 3.6
Final 13.9 12.9 13.2 11.22 12.36
Volume 10.6 8.80 9.4 8.82 8.76
Average Volumes:
Tablet type: Average Volume:
Rennie 17.25
Tesco 7.6633333
Tumms 8.7933333
Calculations:
To find out the concentration of CaCO3 in each tablet we used the method
below:
Key:
M1 = Molarity (concentration) of CaCO3
M2 = Volume of CaCO3 = 25ml
N1 = Balancing Number of CaCO3 = 1
M2 = Molarity (concentration) of HCl = 0.1ml
V2 = Volume of HCl = *Average result (ct2dp)
N2 = Balancing Number of HCl = 2
M1 = M2 x V2 x N1 = 0.1x result x 1 = M1 = (result) M
N2 x V1 2 x 25
Rennie:
M1 = 0.1 x 17.25 x 1 = 1.752 = 0.0354
2 x 25 50
Therefore, the concentration of CaCO3 in Rennie is: 0.034M (ct3dp)
Tesco:
M1 = 0.1 x 7.66 x 1 = 0.766 = 0.01532
2 x 25 50
Therefore, the concentration of CaCO3 in Tescos is: 0.015M (ct3dp)
Tumms:
M1 = 0.1 x 8.79 x 1 = 0.879 = 0.01758
2 x 25 50
Therefore, the concentration of CaCO3 in Tumms is: 0.018M (ct3dp)
Tablet type: Concentration of CaCO3:
Rennie 0.034M (ct3dp)
Tesco 0.015M (ct3dp)
Tumms 0.018M (ct3dp)
Conclusion:
From doing this experiment I have learnt that the tablet which had the highest
concentration of CaCO3 (Calcium Carbonate) was Rennie. Rennie had the highest
molarity and so, was the most effective antacid tablet. This is because it
contained more CaCO3 which meant it had more alkali in it, and it is the alkali
that neautralises the HCl (Hydrochloric acid) which attacks the stomache lining.
These were our results from which you can clearly see that Rennie was the best
antacid tablet to use:
Tablet: Average:
Rennie 17.25 (ct2dp)
Tesco 7.66 (ct2dp)
Tumms 8.79 (ct2dp)
From the results you can see that Rennie is the strongest. Tumms in comparison
to Tescos is roughly 16% more effective because Tumms contains more CaCO3
than Tescos. Rennie is the most effective antacid tablet because it would attack
the excess HCl in the stomache, decreasing the volume of excess acid more
rapidly compared to Tescos and Tumms.
By doing our experiment it helped us by showing us which tablet worked best
and was most effective in neautralising the acid. This experiment showed us how
a tablet would work inside a stomache, it would get rid of the excess acid which
would neautralise more Hydrochloric acid.
Our equation for neautralisation:
Calcium Carbonate + Hydrochloric acid ---> Calcium Chloride + Water
+ Carbon Dioxide
CaCO3 + 2HCl ---> CaCl2 + H2O + CO2
If someone was to ask me for a tablet which would be most effective in getting
rid of stomache aches, I would reccommend that they use Rennie because it is
clearly the best antacid tablet and it would neautralise the acid in the stomache
more effectively. I would also tell them that if they cannot get hold of Rennie
then to use 2 Tesco tablets because they contain less CaCO3 but are cheap.
My prediction for this experiment was correct because I had predicted that
Rennie would be the most effective tablet because it contained MgCO3 and the
most CaCO3, and the more CaCO3 there is, the quicker the neautralisation would
take place and your stomache ache would go quicker.
Evaluation:
The results we obtained were accurate because when we were testing each tablet
we carried on testing until we got 3 results which were within 0.1ml of each
other. We used a burette so we could measure to exactly 0.05ml and also a
pipette which measured to exactly 25ml.
The equiptment which we used were accurate and we also made sure to use
accurate measurements. If any problems were to effect our results, it would be
the funnel which was quite often left in the burette, which could have let drips
through. We recieved 5 results for each tablet and 2 results of each tablet were
anomalous and we chose not to use these because they were not in 0.1ml of
each other. The reason that they were anomalous, could have been because we
had left the funnel in or because of inaccurate measurements:
Tablet Anomalous 1 Anomalous 2
Rennie 21.4 22.5
Tesco 9.1 8.7
Tumms 10.6 9.4
Also, antacid tablets are not designed to be dissolved in water but in saliva and
around acidic solutions, so our results might have been slightly less effective than
what it really would be like. Whilst doing this experiment, we had to make sure
we used 1g of each crushed tablet because each tablet was of different sizes and
weights and by taking 1g pf each tablet our results would be fair.
To make our method more accurate we could test each tablet on people who
have stomache aches and see which one is more effective. We could also test the
pH of a stomache and see which tablet would be most suitable.
Another improvement to our experiment would be to get slices of the stomache
and let it grow to see what happens and then test the tablets. We could also do
the test more times and see if we get the same results.
By Sejal Madlani
