ana chem lab 3b

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:

ana chem lab 3b

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