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Analysis of an Antacid
Purpose

To determine how many times its own mass in excess stomach acid an
antacid tablet will consume

Introduction

The human stomach contains hydrochloric acid,which acts directly on
ingested food and activates the enzyme pepsin for digesting protei ns.
Stomach acid is approximately 0.1 mol/L hydrochloric acid. Excessive
secretion of stomach acid causes theacidity of the stomach to become so
great that the pH of the contents of the stomach falls below 3.0. Antacids
are compounds that reduce the amount of acid in the stomach. An antacid
is said toconsume excess stomach acid when it maintains the pH of the
stomach at 3.0 even if more acid is secreted into the stomach.
In this experiment, 0.100 mol/L hydrochloric acid is used to simulate
stomachacid. A crushed antacid tablet is added to 100 g of the stomach
acid. An acid-base indicator is added to the acid-antacid mixture. The
antacid will neutralize some of the stomach acid, but thecolour of the
indicator indicates that the pH remains acidic, that is, there is still an
excess of stomach acid.
Sodium hydroxide having the same concentration as the hydrochloric acid is
thentitrated into the mixture until the indicator changes colour. The
volume of the sodium hydroxide used in the titration will neutralize the
same volume of hydrochloric acid. The sodium hydroxide neutralizesthe
hydrochloric acid that the antacid leaves unreacted. The larger the
quantity of hydrochloric acid neutralized by the antacid, the smaller the
quantity of sodium hydroxide required toneutralize the remaining acid.

100 mL graduated cylinder
250 mL Erlenmeyer flask
mortar and pestle
50 mL buret

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buret clamp
ring stand
150 mL beaker
250 mL beaker

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phenol redantacid tablets

Materials
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0.100 mol/L hydrochloric acid
0.100 mol/L sodium hydroxide

A. Use a 100 mL graduated cylinder and carefully measure exactly 100 mL
of hydrochloric acid....