Acid Titration Lab Report

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Experiment 7: Titration of an Antacid
Objective: In this experiment, you will standardize a solution of base using the analytical technique known as titration. Using this standardized solution, you will determine the acid neutralizing power of a commercially available antacid tablet.
Introduction
An understanding of the properties of acids and bases is an essential part of understanding chemical reactions (see Tro, pp 167-171). In aqueous solutions, a compound that produces H+ ions upon dissolution is termed an acid. A compound that produces OH– ions when dissolved in water is called a base. The reaction of an acid and base is a neutralization reaction, the products of which are a salt and water. In an aqueous solution, virtually all of the

Thus, about 0.002 moles, or 0.4 g, of KHPh is needed.
At the endpoint, the number of moles of NaOH equals the number of moles of
KHPh used:
MNaOH = moles KHPh Eq. 2
VNaOH in liters or MNaOH = g, KHPh x 1000 mL/L Eq. 3
204.23 g/mole mL, NaOH
Once the NaOH solution has been standardized, it can be used to determine the acid neutralizing capacity of an antacid tablet.
Determination of the Acid Neutralizing Capacity of an Antacid Tablet
The stomach has an acidic interior generated by dilute HCl, “stomach acid”, which insures proper digestion. When the acidity of the stomach becomes high enough to cause discomfort, brought about by the ingestion of certain types of food, an antacid preparation can be taken to neutralize the excess stomach acid. The active ingredient in every antacid is a base, the most common being metal hydroxides, metal carbonates or a mixture of the two. Table 1 lists the active ingredients in several commercial brands of antacid. Table 1. Brands of antacid tablets and their major ingredients
Brand Name Major ingredient Recommended dose
Alka-Seltzer NaHCO3 1 or 2 tablets
Gelusil Al(OH)3; Mg(OH)2 2-4 tablets
Phillips ' Magnesia Mg(OH)2 2-4 tablets
Maalox Al(OH)3; Mg(OH)2 2

The buret is filled to a point above the "0" mL mark with NaOH solution.
In order to fill the tip of the buret with liquid, the solution is drained out of the bottom until the meniscus lies between the "0" and "1" mL marks. The initial buret reading can now be recorded to the nearest 0.01 mL. If you have any doubts as to your ability to read the buret correctly, ask your instructor to check your initial reading.
Standardization of NaOH solution
Accurately weigh out a sample of approximately 0.3-0.4 g of primary standard potassium hydrogen phthalate, KHPh, which has been previously dried at 120°C. Do not use more than 0.4 g. To obtain an accurate mass, weigh the sample on weighing paper, slide it into a clean (but not necessarily dry) 250 mL Erlenmeyer flask and reweigh the paper to account for any KHPh that may remain on it.
Dissolve the KHPh sample in about 50 mL of CO2-free water and add 2-3 drops of 0.1% phenolphthalein indicator. Begin adding the approximately 0.1 M sodium hydroxide solution from the buret while continuously swirling the flask contents. Do not open the stopcock completely. As the endpoint nears, a pink color will appear at the point where the NaOH mixes with the flask contents. This color will disappear