Question

Antacids are compounds, usually bases, used to decrease the amount of hydrochloric acid in the stomach. Write a brief titration procedure for determining how many moles of acid a single antacid tablet would neutralize. This procedure should be detailed and correct so that someone could go into a laboratory and follow the procedure you have written.

Answer 1

First of all you have to consider the teoric value of the antiacid in order to titrate with the appropriate concentration of acid, in this case HCl. For example, the teoric value of antiacid Al(OH)3 is 5mg. Then, we calculate the molarity of titrating solution:

0.005g x 1mol/78g x $0.005g Al(OH)3x \frac{1molAl(OH)3}{78gAl(OH)3} x \frac{3molHCl}{1mol Al(OH)3} x \frac{1molHCl}{0.025L} = 7.69x10^-3 M$

-Prepare the HCl 2.56x10^-3 M solution with the solutions available in your laboratory.

-Take one tablet of antiacid and put it in an beaker of 500 ml.

-Add 100 ml of deionized water to the beaker

-Put a magnetic capsule stirrer and the flask on the magnetic plate

-Add two drops of acid base indicator corresponding to the pH equivalence point is. We will use methyl red which also, is suitable for a weak base strong acid titration.

- To perform the titration is important to rinse the burette with deionized water and then add some quantity of the titrant. Open the stopcock to drained up the content.

-Secure the burette with the clamp  and fill the burette with the HCl 7.69x10^-3 M solution.

-Put the analite beaker underneath the burette.

-Start titration.