Comparing Antacid Neutralization Capabilities

Comparing Antacid Neutralization Capabilities

Objectives

(1) To use back titration to determine the acid neutralizing capabilities of two over-the-counter heartburn medications.

(2) To use LoggerPro pH meter to determine the degree to which they change the pH of an acid solution of known concentration and the time it takes to accomplish that change.

Procedure

Part One

One Alka Seltzer tablet was crushed into a fine powder with a mortar and pestle. A portion of the tablet was massed and dissolved in a beaker containing a solution of about 20 mL of water and 7.00 mL of 1.2 M HCl solution. Three drops of bromomethyl blue indicator were added to the solution.  The beaker was then placed on a hotplate with a stir bar and was gently heated and stirred to drive out carbon dioxide gas and to ensure complete dissolution of the tablet.

A titration apparatus was set up with a burette containing  0.2 M NaOH solution. The sample solution was then titrated to the point of color change (yellow to blue) with the NaOH. The volume of titrant was recorded. The procedure was repeated for Tums.

Part Two

​Tums tablets were crushed into a fine powder. Samples of powder were massed and set aside. A small volume of 1.2 M HCl was placed in a beaker. A volume of water was added to bring the total volume of solution in the beaker to 10.0 mL. A pH meter was connected to a computer running LoggerPro and the sensor was placed in the solution. Time and pH were recorded starting before adding the antacid powder. The recording continued until the pH stabilized. Trials were run for 1.0, 2.0 and 3.0 mL of HCl solution.

Data

Table One: Preliminary Data

trial

mass sample (g)

mL 1.2M HCl

moles HCl

mL 0.2M NaOH

moles NaOH

moles HCl neutralized by sample

Alka Seltzer 1

0.531

7.00

0.00840

44.34

0.00887

-0.000468*

Alka Seltzer 2

0.995

7.00

0.00840

37.97

0.00759

0.000806

Tums

0.500

7.00

0.00840

23.64

0.00473...