Post on 03-Jun-2018
8/11/2019 ana chem lab 3b
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in digestion and also kill bacteria the acid is highly corrosive and may cause ulceration or heart
burn. There is a mucus barrier which protects the lining of the stomach, if this mucus membrane
is damaged the stomach lining will be exposed to the acid and this results in ulcers. The antacid
works by neutralizing the acid so as to make it less corrosive, this helps to prevent the ulcers and
gastritis and heart burn. The reach reaction between the antacid and the stomach acid HCL is a
acid base reaction. Majority of antacids contain weak bases, true a chemical reaction they
neutralize the stomach acid the most common bases which antacid contains include: magnesium
hydroxide, aluminium hydroxide, sodium bicarbonate and calcium carbonate. Acid and bases
react to produce salt and water, example of the chemical reaction is magnesium hydroxide plus
hydrochloric acid produces magnesium choride and water. Antacids are insoluble and in the case
that carbon dioxide is produced they are analysed by a method known as back titration. The
antacid is allowed to react with a known amount of HCL and the excess HCL is titrated with
excess sodium hydroxide. The amount neutralized by the antacid is determined by the excess
moles minus the initial moles to give moles neutralized. If there is carbon dioxide production in a
reaction of an antacid, the carbon dioxide must be removed before titration this gas can be
removed by boiling which will shift the equilibrium in the reaction below to the left:
CO2+ H2O HCO1-
3(aq) + H1+
(aq)
If CO2is left dissolve, the H+ produced would be titrated by sodium hydroxide.
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Results:
TABLE 1- SHOWING MASS FOR KHP
1 2 3
Mass of beaker
+solid(g)
33.8645 33.7434 32.7501
Mass of beaker(g) 33.3042 33.2211 32.1985
Mass of solid(g) 0.5603 0.5223 0.5516
TABLE 2-SHOWING BURETTE READINGS FOR STANDARDISATION OF NAOH
Mass of KHP(g) 0.5603 0.5223 0.5516
Initial vol of
NaOH(ml)
4.46 4.08 2.51
Final vol ofNaOH(ml)
33.48 31.21 30.81
Titre vol ofNaOH(ml)
29.02 27.13 28.30
Observation: Solution changed from colourless to pink
TABLE 3- SHOWING MASS FOR ANTACID TABLETS
Mass of watch glass + tablets(g) 39.8185
Mass of watch glass(g) 37.3309
Mass of tablets(g) 2.4876
Avg mass of one tablet(g) 0.8292
TABLE 4- SHOWING MASS FOR CRUSHED ANTACID TABLETS
1 2 3
Mass ofbeaker+antacid(g) 34.4648 33.8068 33.7431
Mass of beaker(g) 33.9211 33.2854 33.2014
Mass of antacid(g) 0.5437 0.5214 0.5417
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TABLE 5- SHOWING BURETTE READINGS FOR STANDARDISATION OF HCL
Volume of HCL(ml) 25 25 25
Initial vol of
NaOH(ml)
4.22 2.78 4.21
Final vol ofNaOH(ml) 29.96 28.61 30.09
Titre vol of
NaOH(ml)
25.74 25.83 25.88
Avg titre vol of
NaOH(ml)
25.82
Observation: Solution changed from colourless to pink
ANALYSIS OF ANTACID
TABLE 6- SHOWING BACK TITRATION WITH NaOH
Mass of antacid(g) 0.5437 0.5214 0.5417
Vol of HCL used(ml) 50 50 50
Initial vol of
NaOH(ml)
2.92 2.13 2.51
Final vol of NaOH
(ml)
42.89 41.51 42.52
Titre vol of
NaOH(ml)
39.97 39.38 40.01
Observation: Solution changed from cloudy to pink
Discussion: In this experiment the boiling of the antacid solution wasnt necessary because
there was no carbonate present in the sample hence, carbon dioxide was absent. A limtitation
could be that the antacid was not fully dissolved if the solution was boiled the antacid would
have dissolved.
In order to know the effectiveness of antacid, the amount of hydrochloric acid neutralized was
normalized to the mass of tablet. The larger the normalized value, the more effective the antacid.
Conclusion: