Index

 Aim of the project

 Introduction

 Theory

 Requirements

 Procedure

 Observation

 Result

 Bibliography
Aim:
To analyze the given samples of commercial antacid by determining the
amount of hydrochloric acid they can neutralize.
Introduction:

∞ It is well known that the food we take undergoes series of complex reaction
within the body which constitute digestion and metabolism. These
reactions are catalyzed by enzymes which can function properly only
when the pH of the medium is within a specific range.
∞ Some enzymes require mildly alkaline conditions while other operate only
in weakly acidic media. The enzymes control the digestion of proteins
present in the food as it reaches the stomach. In the stomach dilute HCl
is secreted and it provides mildly acidic conditions required for the
functioning of protein digesting enzymes in the stomach.
∞ Gastric acid is a digestive fluid formed in the stomach. It has a pH value
of 1.5-3.5 and is composed of 0.5% hydrochloric acid (HCL). It is produced
by cells lining the stomach.
∞ Other cells in the stomach produce bicarbonate to buffer the acid, ensuring
the pH does not drop too low. Also, cells in the beginning of the small
intestine or duodenum produce large amount of Bicarbonate to completely
neutralize any gastric acid that passes further down into the digestive tract.
A thick coat of mucus forms a vicious physical barrier to prevent gastric
acid from damaging the stomach.
∞ However sometimes the stomach begins to secrete and excess of HCL.
This led to a condition known as gastric hyper acidity. This condition can I
also be Triggered by the intake of too much food which makes the stomach
to secrete more acid resulting in hyper acidity.

∞ To counter this situation substance like antacid are used. Antacids are
commercial products that neutralize the excess acid in the stomach
providing relief to the people. Antacid is based on the concept that a base
can neutralize an acid forming salt and water.

∞ Antacids must have to satisfy the condition - right amount of alkali. If the
content of the alkali is too high it will replace acidity and create alkaline
condition that makes the digestive enzymes ineffective.
∞ To make sure that the pH of the stomach remains in a specific range, many
substances are added to the antacids.

Theory:
∞ Antacids react with excess stomach acid by neutralization
HCI + NaOH→ H2O + NaCl
∞ During the process, hydrogen ions H+ from the acid (proton donor) or a
hydronium ion H3O+ and hydroxide ions OH- from the base (proton
acceptor) react together to form a water molecule H2O.
∞ In the process, a salt is also formed when the anion from acid and the
cation from base react together. Neutralization reactions are generally
classified as exothermic since heat is released into the surroundings.
∞ Acids are proton donors which convert into conjugated bases. They are
generally pure substances which contain hydrogen ions (H+) or cause
them to be produced in solutions.
∞ Hydrochloric acid (HCI) and sulfuric acid (H2SO4) are common
examples. In water, these break apart into ions:
HCl→ H+(aq) + Cl- (aq)
(OR)
H₂SO₄ → H+(aq) + HSO4- (aq)
∞ Bases are proton acceptors which convert into conjugated acids. They
are generally substances which contain hydroxide ion (OH-) or produce it
in solution.
∞ Alkalis are the soluble bases, i.e. a base which contains a metal from
group 1 or 2 of the periodic table. To produce hydroxide ions in water,
the alkali breaks apart into ions as below:
NaOH→ Na+(aq)+OH-(aq)
∞ Examples of bases include sodium hydroxide (NaOH), potassium
hydroxide (KOH), magnesium hydroxide (Mg (OH)2). and calcium
hydroxide (Ca (OH)2) Antacids are generally bases.

Requirements:
a. Apparatus:

 Burette(50ml)
 Pipette(20ml)
 Conical Flasks (250ml)
 Measuring Cylinder(10ml)
 Beakers(100ml)
 Standard Flasks (100ml)
 Filter Paper
 Funnel
  Bunsen Burner
 Weighing machine
 Clean & glazed white tile
 Glass Rod
 Water
 Crusher
b. Chemicals:

 NaOH powder
 Na CO powder
2 3

 10M conc. HCl acid

 Four different brands of antacids
 Phenolphthalein
 Methyl Orange
Procedure:

† First prepare 1 litre of approximately N/10 solution of HCI by diluting

10ml of the given 10M HCI acid to 1litre.
† Next prepare 1 litre of approx. N/10 NaOH solution by dissolving
4.0g of NaOH to make 1 litre of solution.
† Similarly prepare N/10 Na₂CO3 solution by weighing exactly 1.325g
of anhydrous Na2CO3 and then dissolving it in water to prepare
exactly 0.25L or 250 ml of Na₂CO3 solution.
† Now, standardize the HCl solution by titrating it against the standard
Na₂CO3 solution using methyl orange as indicator.
† Similarly standardize the NaOH solution by titrating it against
standardized HCl solution using phenolphthalein as indicator. Stop
the titration when the pink colour of the solution disappears.
† Now, powder the four antacid samples and weigh 0.5 g of each.
 † Add 25 ml of the standardised HCI to each of the weighed samples
taken in conical flasks. Make sure that the acid is in slight excess so
that it neutralizes all the basic character of the tablet powder.
† Add a few drops of phenolphthalein indicator and warm the flask
over a Bunsen burner till most of the powder dissolves.
† Filter the insoluble material.
† Titrate this solution against the standardized NaOH solution till a
permanent pinkish tinge is obtained.
† Repeat the same experiment for all other samples too.

Observations:

‡ Standardisation of HCl solution:

Volume of 0.1N Na2CO3 taken is 20ml
Indicator used is Methyl Orange.
Serial Burette initial reading Burette final reading Volume
No. of acid
0 17 17
1.
18 35 17
2.
Applying normality equation,
N1 V1 =N2 V2
N1 x 17 = 0.1 x 20
Normality of HCl, N1 = 2/17 = 0.11 ≈ 0.1
‡ Standardization of NaOH Solution:
Volume of the given NaOH solution taken is 20.0 ml

Indicator used is phenolphthalein

Burette initial reading Burette final reading Volume
Serial of acid
No.
 0 16 16
1.
17 33 16
2.
Volume of acid used = 16 ml
Applying normality equation,
N1 V’1 = N2 V’2
0.11 x 16 = N’2 x 20
Normality of HCl, N’2 = (0.11*16)/20 = 0.09 ≈ 0.1

antacid Volume (NaOH) used for

neutralizing unused (HCl)
1. Eno pineapple 29
2. Eno lemon 24
3. Digene 9
4. Omez 24
5. Pephyrous 40
6. Gelusil 22

Result:

† 1 g of Eno Pineapple required 29 mi of Sodium Hydroxide

(NaOH) to titrate it completely.
† 1 g of Eno Lemon required 24 ml of Sodium Hydroxide
(NaOH) solution to titrate it completely.
† 1 g of Digene lime required 9 ml of Sodium Hydroxide
(NaOH) to titrate it.
† 1 g of Omez required 24 ml of Sodium Hydroxide (NaOH)
to titrate it completely.
† 1 g of Pephyrous required 40 ml of Sodium Hydroxide
(NaOH) to titrate it completely.
† 1 g of Gelusil required 22 ml of Sodium Hydroxide (NaOH)
to titrate it completely.
 † Based on the hypothesis of the experiment, the antacid
which requires the least amount of Sodium Hydroxide
(NaOH) is the best antacid. From the recorded observation,
Digene requires the least (5 ml), and is therefore the best
Antacid.

BIBLIOGRAPHY
◊ http://www.reachoutmichigan.org/funexperiments/quick/csustan/antacid

◊ http://ien2.uneche.maine.edu/genchemlabs/Antacid/antacid2.htm

◊ http://www.chem.latech.edu/~deddy/chem104/104

◊ http://www.images.google.com

◊ http://www.wikipedia.com