Antacid Effectiveness

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Feb 20, 2024

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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

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.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

III. Back ?tra?on Answer the following ques?ons as a group: You may add space as needed to answer the ques(ons 4. Write the neutralizaJon reacJon occurring during the JtraJon of the over-neutralized soluJon of the original antacid tablet with NaOH(aq)? (3 points) H2CO3(aq) + 2NaOH(aq) = Na2CO3(aq) + 2H2O(l) 5. From the list of phenolphthalein, bromothymol blue, phenol red, methyl orange, and methyl red, what indicator are you choosing for your JtraJon? Brieﬂy explain, considering the colors involved and the expected equivalence point pH. (3 points) We are using phenolphthalein because it is expected that the NaOH 5tra5on equivalence range will be between 8-10 which is the transi5on range for phenolphthalein. 6. Given the concentraJon in Table 2, what volume of NaOH(aq) do you expect will be needed to back Jtrate your over-neutralized and dissolved antacid sample? Brieﬂy explain or show work. (3 points) HCl(aq) + NaOH(aq) = NaCl(aq) +H2O(l) 10 mL HCl (1L / 1000 mL)(1.48 mol HCl / 1 L)(1 mol NaOH / 1 mol HCl)(1L / 1.04 NaOH)(1000 mL / 1 L) = 14.23 mL NaOH Experiments to be carried out individually: 2. Aoer your soluJons have cooled, add three to four drops of the indicator you have chosen to the first of your over-neutralized antacid soluJons. 3. Titrate your soluJons with NaOH to the endpoint. Periodically rinse the sides of your Erlenmeyer ﬂask with DI water to assure complete reacJon of all of the antacid soluJon and all the Jtrant Record your results in Table 5. Also record your confidence idenJfying the equivalence point without overshooJng; mark the last column with an H=high, M=medium, or L=low confidence. 4. From your iniJal and final buret volumes, determine the vol of NaOH added, and using the concentraJons in Table 2, determine the mol NaOH added. Record this in Table 5. 5. Repeat steps 2 and 3 for your other two samples adding the data to the table. 6. Aoer you are saJsfied with your experiments, carefully drain and rinse burets to make sure they are clean. You can check residual water drops on the buret with pH paper to

see if you have fully rinsed away all the acid or base it contained. Dispose of excess reagents and reacJon products in labelled waste containers and clean all vessels. Table 5. TitraJon results. (4 points) 2 H: high, M: medium, L: low IV. Data Repor?ng Fill out the reporJng excel worksheet using data from Tables 4 and 5. Submit one reporJng worksheet for your group to Canvas. V. Calcula?ons Q7. Show calculaJons for the following quanJJes and record the results for each tablet in Table 6. • moles HCl neutralized for each tablet from the moles of acid originally added to dissolve the sample and the mol of NaOH added during the back JtraJon. (2 points) M1V1 = M2V2 (1.04 M NaOH)(.01545 L) = (1.48 M HCl)(V2) V2 = 0.01086 L HCl Mol HCl = (0.01086 L HCl)(1.48 M HCl) Mol HCl = 0.01607 • the mass of HCl neutralized / tablet. (2 points) g HCl = 0.01607 (36.458 g HCl / 1 mol HCl) g HCl = 0.5859 mg HCl = .5859 g (1000g / 1g) mg HCl = 585.9 • the neutralizing power per cost of tablet (mg HCl neutralized / cents) (2 points) Neutralizing power per cost of tablet = 585.9 mg / 1.3 cents Buret volume (mL) vol. NaOH(aq) added (mL) mol NaOH added Confidence in JtraJon 2 IniJal Final Tablet 1 0 16.5 16.5 .01716 H Tablet 2 0 14.6 14.6 .01518 M Tablet 3 0 15.1 15.1 .01570 H Tablet 4 0 16.5 16.5 .01716 M Tablet 5 0 15.5 15.5 .01612 M Tablet 6 0 14.5 14.5 .01508 M

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Neutralizing power per cost of tablet = 450.7 mg/cents • also calculate (do not need to show work) the average and standard deviaJon for each of these quanJJes and record in Table 6. Do not include in the average and standard deviaJon tablet results that you had a low confidence in idenJfying the endpoint. Note that you can enter the informaJon in to an excel sheet to easily calculated the average and standard deviaJon. Table 6. Summary of results on the neutralizing capacity of the antacid studied (4 points). 1 Do not include results with low confidence in endpoint determinaJon. VI. Conclusions from data: Table 7. Summary of Class Data (provided when available) (4 points) Mol HCl neutralized/ tablet Mass HCl neutralized / tablet Mass HCl neutralized / cents Tablet 1 .01716 652.6 502.0 Tablet 2 .01518 553.4 425.7 Tablet 3 .01570 572.4 440.3 Tablet 4 .01716 625.6 481.2 Tablet 5 .01612 587.7 452.1 Tablet 6 .01612 587.7 452.1 Average 0.0162 597 458.9 Standard DeviaJon 7.23eE-4 33.0 25.48 Mol HCl neutralized/ tablet Mass HCl neutralized / tablet Mass HCl neutralized / cents Equate 0.01530 558 ± 77 429.2 Bimart – reg. str. 0.009874 360 ± 17 200.7 Bimart – extra str. 0.0151 549 ± 68 140.8 Tums 0.0151 550 ± 19 110.2 Walgreens 0.00993 362 ± 28 98.9 Goodsense 0.0114 416 ± 101 171.0

Ques?on to answer as a group: Q8-Q10 will be graded based upon: • Your responsiveness to the ques(on including providing the specific data needed for the comparison as part of the answer to your ques(on. • The accuracy of your response. • The inclusion of uncertainty in your comparison. • The discussion of any poten(al discrepancies. You may add space as needed to answer the ques(ons Q7. Do your group’s results agree with the class data for the same antacid you studied? (3 points) Our group recorded an average of 0.0162 +/- 7.23E-4 mols HCL neutralized while the class data was an average 0.01530 mols HCl neutralized (tables 6 and 7). Our recorded average mostly agrees with the class data however the slight difference is most likely due to slight over 5tra5ons in our group. For mass HCl neutralized per tablet we recorded 579 +/- 33.0 mg of HCl neutralized for Equate (table 6). The class data for Equate shows an average of 558 mg of HCl neutralized with a standard devia5on of 77 mg (table 7). The recorded mass of HCl neutralized for Equate agrees with the class data as it is reasonably close to the class average and well within one standard devia5on of the class mean. Our group also recorded an average mass HCl neutralized / cents to be 458.9 +/- 25.48 mg / cent while the class data shows an average of 429.2 mg HCl neutralized / cent (table 6 and 7). Our recorded value was slightly higher than the class average which is understandable since the mass of HCl neutralized per tablet for our group was also higher than the class average. Again, any observable differences between class data and our groups data are a[ributed to error such as incorrectly reading bure[e volume or over 5tra5ng. Q8 . Based on the class data, is the amount of acJve ingredient reported for the antacids accurate? (3 points) Based on the class data the amount of ac5ve ingredient reported in the antacids are not accurate. In the class data only two out of the six antacids reported accurate values of total antacid. Equate and goodsense and good sense reported values of 558 ± 77 and 416 ± 101 which both fall well over the reported values. For the other 4 antacids, they don’t go much higher than 200 lower than the reported values. For example Bi-mart regular strength has a reported 500 mg but the class data was 360 ± 17 showing a significantly less amount of antacid present. Then there is Tums which has 550 ± 19 when the reported value was 750 mg. These lab tested values may vary from the actual quan5ty of antacid in the tables due to some lab errors such as improper 5tra5ons, which would affect the calculated quan5ty of antacid. Overall though based off the class averages the amount of ac5ve ingredient is less than the reported quan55es of antacid.

Q9. Based on the class data, which antacid is the greatest value? (3 points) Equate has the greatest value based on the class data. Equate not only neutralizes the most HCl per tablet at 558 +/- 77 mg HCl neutralized / tablet but also neutralizes more HCl per cent at 429.2 mg HCl / cent (table 7). However, it is important to note that Equate has the second largest standard devia5on of all the antacids measured at 77 mgs for mass HCl neutralized per tablet (table 7). For example, Tums has an average mass (mg) HCl neutralized per tablet of 550 with a standard devia5on of only 19. Equate is on average the best value out of the antacids measured but it also has a rela5vely high varia5on in results when compared to the other antacids. Q10. IdenJfy two possible sources of error in the experiment. For each, state whether they would result in your determinaJon of the mass of HCl neutralized per tablet to be too high or too low or simply less precise. Include brief logic supporJng your conclusions. (3 points) The first possible error that One possible source of error could be inaccurately measuring your volume for NaOH and HCl. If you were to mess-up on recording the ini5al and final volumes, that mistake would throw off all the subsequent calcula5ons about the quan5ty of HCl neutralized. If too much HCl was put in to neutralize the tablet and then an improper amount of NaOH was used to reduce it for example medium confidence examples, that would cause the HCl results to be less accurate and lower than expected A second possible source of error in the experiment would be not completely dissolving the quan5ty of the tablet. In the experiment for one of the trails with low confidence the tablet would not completely dissolve meaning that there would be excess HCl used to neutralize the weak base causing the accuracy to be lower and the amount of HCl needed to neutralize a tablet would be too low.

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