BEHS Chemistry |
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Assignment directions for a project measuring the effectiveness of antacid Manager of Chem Projects CheMystery Labs 380 South Buzz Blvd Bee Hive, UT 84302 Dear Manager: A consumer group, Truth in Advertisements, would like to check the claims made by various antacid manufactures. Which antacid is the most effective in neutralizing excess stomach acid? What antacid is the most cost effective in neutralizing stomach acid? The group has given a budget of $80,000 to answer their question. Before you begin your work, I will need the following information from you so that I can approve your work. The planning space for these items is found in your project packet. Ø a detailed summary of your hypothesis, experimental design table, a plan for the procedures along with all necessary data tables Ø a description of necessary calculations Ø an itemized list of equipment with costs and chemical with their costs, include labor costs of $80 / hour and cost for laboratory space $10,000/day, and a standard disposal fee of $2000 / gram of material. After you complete the analysis, prepare a report for the group, Truth in Advertisements. Remember that this report will be seen by a variety of people, so be certain it projects the image we want to present. The items that should be included in the report are found in your project packet. Good luck with the project. Please keep in close contact me as you proceed with the project. You will need a data verification signature, by having me observe one of the trials in the experiment. Sincerely Your teacher President and CEO CheMystery Labs Inc. Which brand of antacids( ) neutralizes the most stomach acid and which of the brands tested is the most cost effective? Background The the human digestive system makes use of hydrochloric acid in the breakdown of food. Gastric fluid (stomach acid) is estimated to have a pH of one. This is equivalent to a concentration of 0.10 M HCl. Antacids are used to reduce stomach acid when it is in excess. The makeup of antacids varies greatly depending on the manufacturer. Sodium hydrogen carbonate is used in Alka Seltzer. Calcium Carbonate is used in Tums, Alka-2, and Di-Gel liquid. Rolaids contains the substance aluminum sodium dihydroxy carbonate. Sodium-free Rolaids contains calcium carbonate and magnesium hydroxide. Milk of Magnesia is mostly magnesium hydroxide. Each of these substances will react to neutralize excess stomach acid.
Antacid preparations are sold over the counter for relieving heartburn or acid indigestion. These symptoms are caused by excess stomach acid, which, for the purposes of this experiment, we can conveniently think of as being pure hydrochloric acid (HCl). Antacids contain basic substances that either neutralize the excess acid or act as buffers in the stomach. The types of bases commonly used in actacids include metallic hydroxides, metallic carbonates, or hydrogen carbonates. The net ionic equation for the neutralization of magnesium hydroxide, Mg(OH)2, a typical metallic hydroxide used in antacids, is shown in equation 1. (Eq. 1) Mg(OH)2(s) + 2 H3O+(aq) ---------> Mg2+(aq) + 4 H2O(l)
In this reaction, 2 mol of hydronium ions (H3O+) react with 2 mol of hydroxide ions (OH-). Thus, 1 mol of hydroxide ions neutralizes 1 mol of H3O+ ions. When calcium carbonate (CaCO3), a typical metallic carbonate used in antacids, neutralizes HCl, it involves a two-step process, as shown in Equations 2 and 3. (Eq. 2) CaCO3(s) + 2 H3O+(aq) --------> Ca2+(aq) + H2CO3(aq) + H2O(l) (Eq. 3) H2CO3(aq) <---------> CO2(g) + H2O(l) In the reaction in Equation 2, 1 mol of carbonate ions (CO32-) neutralizes 2 mol of H3O+ ions. Example of the buffering action of antacids are developed in Equations 4-6. Equation 4 shows the reaction (Eq. 4) CO32-(aq) + H3O+(aq) <--------> HCO3-(aq) + H2O(l) Hydrogen carbonates ions (HCO3-) can react with either OH- ions or H3O+ ions, as shown in Equations 5 (Eq. 5) HCO3-(aq) + OH-(aq) <--------> CO32-(aq) + H2O(l) (Eq. 6) HCO3-(aq) + H3O+(aq) <--------> CO2(g) + 2 H2O(l) Thus, the combination of HCO3- and CO32- ions in antacid tablets serves to neutralize acid and to establish One method of evaluating antacid preparations is to determine the number of mL of HCl that will react with In general, we can calculate N, the number of mL of HCl neutralized by a tablet, using Equation 8, where A (Eq. 8) N = A - B To compare different brands of antacids, we calculate the mass effectiveness and cost effectiveness of each (Eq. 11) E = N / W or/and
We can calculate C, the cost effectiveness of a tablet, which is the number of mL of HCl neutralized per (Eq. 12) C = N / P
In this experiment, you will dissolve a commercial antacid tablet in excess standardized HCl solution. Next, of two common antacids by titrating a known sample of antacid with 0.100 M hydrochloric acid. Using your data and calculations, you can report on the relative effectiveness of your antacids.
TITRATION PROCEDURES 1. Mass tablet and record. (solution should be bright yellow at this point- an Acid solution) 5. Record beginning reading of the buret.
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