Antacid Effectiveness

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University of Oregon *

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229

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Chemistry

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Feb 20, 2024

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Uploaded by CaptainLightning13433

Groups Names: Name1: Name 2: Worksheet for Lab 24. Antacid Effec?veness CH223 – Spring 2023 Lonergan/Clayton Instruc(ons are in italics, and they can be deleted: This is a group worksheet. With that said, every member of the group will complete the laboratory experiments individually. All the data collected by the individual members of the group will be reported on this worksheet. Ques(ons will be answered collec(vely. • Informa(on in square brackets and highlighted yellow should be replaced with the appropriate informa(on: [text to replace] • Make sure to record physical quan((es with units. You can add them to the column heading if appropriate 1. Preparing for lab: Read Lab 24 in your lab manual on pages 221-224

I. Collec?ng background informa?on and preparing for the lab work. Consider the acJviJes of others in the lab to decide the most effecJve way to complete the work below. 1. Each member of the group should individually prepare reagents for their experiments: a. Obtain 60 mL of standardized NaOH(aq) and 80 mL of standardized HCl (aq) in separate beakers. For safe transportaJon and handling, select your beakers so as not exceed 2/3rds of their capacity. Record the concentraJons of HCl and NaOH in Table 2. b. Prepare (condiJon and fill) two separate burets, one with HCl(aq) and one with NaOH(aq). For instrucJons on condiJoning your buret see “The JtraJon procedure” under the “Volumetric Analysis: TitraJon” secJon in the front ma^er of your laboratory manual. 2. Fill out the informaJon in Table 1 using the packaging informaJon provided with the antacids. You will be assigned one, but it is necessary that you have the informaJon on all the antacids to make comparisons with class data. 3. Assign each member of your group a set of three numbers to use in idenJfying the antacid tablets they will be working with. Each member of the group will do experiments on three tablets for up to nine total experiments. Record your assignments in Table 3 below. Table 1. InformaJon on the antacids analyzed. (4 points) 1 Brand Equate BiMart Reg. Str. Bimart Extra Str. Tums Walgreens Goodsense Tablets / package 150 150 96 96 150 150 Cost / package 1.99$ 2.69 2.69 4.79 5.49 3.65 Cost / tablet 0.013$ 0.0179$ 0.028$ 0.050$ 0.037$ 0.024$ AcJve ingredient CaCO3 CaCO3 CaCO3 CaCO3 CaCO3 CaCO3 Mass acJve ingredient (mg) 500 500 750 750 500 500

Table 2. ConcentraJons of reagents used in this lab. (2 points) Table 3. Numbers to be used by each team member.(2 points) II. Over-neutraliza?on and dissolu?on of tablet: Ques?ons to be answered as a group: You may add space as needed to answer the ques(ons 1. What brand of antacid was assigned to your group and what observaJons do you have about your brand of antacid as well as the specific tablets you will be using. (2 points) The brand of antacid is Equate, and the observa5ons about the antacid is that they are white tablets that smell minty, they claim to have 500 mg of CaCO3. Only under certain circumstances will you be assigned Goodsense regular strength peppermint. In general you should be expected to be assigned on of the brands that has color in the tablet. 2. Write the balanced chemical equaJon for a. the neutralizaJon reacJon between HCl(aq) and the acJve ingredient in the antacid to form carbonic acid. (2 points) 1. 2HCl(aq) + CaCO3(s) = H2CO3(aq) + Ca2+(aq) + 2Cl-(aq) b. the decomposiJon of carbonic acid to form CO 2 (g) (2 points) 2. H2CO3 (aq) = H2O(l) + CO2(g) 3. Given the concentraJon in Table 2, what volume of HCl(aq) do you esJmate is needed to completely react with the stated amount of acJve ingredient? Show your work. (3 points) 500 mg CaCO3 (1g/1000mg)(1 mol CaCO3 / 100.09 g CaCO3)(2 mol HCl / 1 mol CaCO3)(1 L / 1.48 mol HCl) = .00675 L Moles of acJve ingredient 0.004996 0.004996 0.007494 0.007494 0.004996 0.004996 NaOH(aq) HCl(aq) concentraJon 1.04 1.48 Delete third team member if not needed Assigned numbers Asa 1-3 Cade 4-6

.00675 L (1000mL / 1L) + 10mL = 16.75 mL HCl needed For a 750 mg Table and a 1.5M HCl(aq) soluJon, this is: 9.99 mL Experiments to be completed individually: 1. Using gloves to prevent contaminaJng the tablet, place one antacid tablet in a 250 mL Erlenmeyer ﬂask. 2. Record the iniJal volume on your HCl(aq) buret. Deliver the volume of HCl(aq) esJmated in Q3 to neutralize the acJve ingredient in the tablet plus 10 mL. Record the final volume. Note that you need to know as precisely as possible the volume of HCl(aq) added, but it does not have to be exactly the amount in Q3 plus 10 mL. The moles of HCl just needs to be suﬃciently in excess that the excess can be back Jtrated to determine the amount of HCl neutralized by the tablet. 3. Repeat steps 1 and 2 for two more antacid tablets so you will have a total of three samples. Make sure to label the ﬂasks and refill the buret before preparing each so that you can deliver the appropriate volume. 4. Warm the Erlenmeyer sample ﬂasks on a hot plate set to medium-low with swirling to dissolve the sample (remember hot glass can burn you and looks like cold glass). A very small amount of the sample may not dissolve and that is OK. Heat the sample further and boil for one minute to drive off dissolved CO 2 . Do not overheat the sample as this can cause the dyes in the tablet to discolor, and darken, making it diﬃcult to see the endpoint in the back JtraJon. 5. Let the soluJons cool for at least 5 minutes. Table 4. Amounts of HCl added to over-neutralize and dissolve the antacid tablets.(4 points) delete tablets 7-9 if not needed 1 should be approximately the volume in Q3 plus 10 mL. Buret volume Volume HCl added 1 mol HCl added IniJal Final Tablet 1 8.2 25 16.8 .02486 Tablet 2 8.2 25 16.8 .02486 Tablet 3 8.2 25 16.8 .02486 Tablet 4 8.18 25 16.82 .02489 Tablet 5 8.2 25 16.8 .02486 Tablet 6 8.25 25 16.75 .02479

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