Experiment #12 - Lab 12 from Chem 106 PDF

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Lab 12 from Chem 106...

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Keyshawn Smith Professor Depouli 11/2/20 Heartburn and “AUNTY ACID” Introduction:  For many years I always wondered why I would always feel heartburn after overeating or when I go along time without eating and my stomach and chest start to pain me out of nowhere, which could be causing that sudden pain. Well, the pain comes from gastric acid that is formed in our stomach and is composed of hydrochloric acid, potassium chloride, and sodium chloride. Gastric acid plays a very important role in our digestion of proteins that activate digestive enzymes to break down long chains of amino acids, but what happens when there is too much of a build-up of gastric acid. An ulcer formation can be formed within the lining of the stomach, but the good thing is all of this can be avoided due to antacids being used to neutralize HCl acid by using the titration method to see which antacid is the most efficient/ effective against gastric acid build-up. Materials:  Tums is one of the antacids that was used within the experiment so that we can observe the concentration but also the mass and cost effectiveness  Weighing Machine used for weighing the weight of antacid  Alka-Seltzer is one of the antacids that was used within the experiment so that we can observe the concentration but also the mass and cost effectiveness  Moore/Alcalak is one of the antacids that was used within the experiment so that we can observe the concentration but also the mass and cost effectiveness  Water used to rinse and wash burette  Sodium Hydroxide is one of the bases used for the solutions which was added to the solution as a base  Hot plate would be used in the actual lab to heat the solution to get it to go the endpoint faster

Experimental and Data: Tria l

1 2 3

Amoun t of Antacid used (g) 0.36 0.37 0.36

Volume of .1 M HCl used (mL) 50 50 50

Mole s of HCl used

Volume of .1M NaOH used (mL)

0.005 0.005 0.005

0.00067 0.00056 0.00069

Moles of NaO H used 6.7 5.6 6.9

Moles of HCl neutralize d 0.00433 0.00444 0.00431

Moles of HCl neutralize d per tablet 0.008178 0.00816 0.008141 Avg.

Mass Effectivenes s (mol/g) 0.01202647 0.012 0.01197205

Cost Effectivenes s (mol per cent) 0.0017732 0.00176929 0.00176517

Trial #1:  Moles HCl= (50 mL/ 1000) = 0.05 L (0.05 L x .1 M HCl) = 0.005 moles of HCl  Moles NaOH= (6.7 mL/ 1000) = 0.0067 L (0.0067 L x .1 M NaOH) = 0.00067 moles of NaOH  Moles of HCl neutralized= 0.005 mols HCl – 0.00067 mols NaOH= 0.00433 mols of HCl neutralized  Moles of HCl neutralized per tablet= (0.00433 moles HCl neutralized x 0.68 grams of tablet)/ (0.36 grams of sample) = 0.008178 mol  Mass Effectiveness= (0.008178 mols/ 0.68 grams) = 0.01202647 mol/grams  Cost Effectiveness= (23.06 x 100 x 1)/ (1 x 500) = 4.612 cents  (0.008178 mol)/ (4.612 cents) = 0.0017732 mols per cents Group

Tablet Type

1 2 3 4 5 Group 106-14

Alka Seltzer Alka Seltzer Alka Seltzer Tums Tums Alcalak

Mass Effectiveness (mol/g) 3.20 x 10^-3 2.00 x 10^-3 1.36 x 10^-3 7.29 x 10^-3 7.39 x 10^-3 1.202647 x 10^-2

Cost Effect (mol per cent) 4.25 x 10^-4 3.00 x 10^-4 1.80 x 10^-4 1.67 x 10^-3 1.70 x 10^-3 1.7732 x 10^-3

Discussion and Conclusion: I noticed that when doing that when working with titration that if we were in an actual lab simulation environment like a laboratory we would have to add a titrant to an analyte, where we would then wait for the point where we observe the endpoint or in other words the point where the endpoint is met.

The indicator phenolphthalein would be an indicator that would potentially change the color of the solution if we were hypothetically in a lab. However, in order to observe whether or not the solution has reached its endpoint we observe whether the color shifts from a very dark color back to a very light color, where equilibrium has been met. Therefore in this lab even though we weren’t in a physical laboratory we used equations such as E= (moles of HCl neutralized per tablet)/ (mass of tablet, g) to find the mass effectiveness, C= (moles of HCl neutralized per tablet)/ (Price per tablet) to find cost effectiveness, M= (mol/ L) to find the Molarity, moles of HCl neutralized= moles of HCl added to antacid – moles of NaOH required to back titrate, moles of HCl neutralized per tablet = (moles of HCl neutralized x mass of tablet)/ (mass of sample). All these calculations were used to help me find the HCl neutralization, mass effectiveness, and cost effectiveness of Alcalak which then illustrated that different antacids will vary in different neutralizations even if they are the same tablet type and the cost effectiveness will vary as well. For example, Alka-Seltzer in group 1 has a mass effectiveness of 3.20 x 10^-3 and cost effectiveness of 4.25 x 10^-4 but AlkaSeltzer in group 2 has a mass effectiveness of 2.00 x 10^-3 and a cost effectiveness of 3.00 x 10^-4 which is slightly lower than Alka-Seltzer in group 1, which makes me question whether or not expiration within or unbalanced concentrations within the tablets plays a role in effecting in mass effectiveness and cost effectiveness because if the tablet is expired that means that it would be toxic to consume and could cause potential health damages therefore, it would make sense for the cost effectiveness and mass effectiveness to be higher since it isn’t good anymore it wouldn’t be able to sell within pharmaceutical stores. References: Smeureanu, G. & Geggier, S. (2019). General Chemistry Laboratory. New York, NY Zumdahl, S. (2014). Chemistry. 9th ed. Belmont, California: Cengage Learning Focus Questions: 1) Which antacid is the most effective in terms of mass?  Alka-Seltzer from group 3 because it has the lowest number for mass effectiveness which illustrates that it neutralized the fastest therefore making it the most efficient.

2) Which antacid is the most effective in terms of cost?  Alka-Seltzer for group 3 was the most effective in terms of cost because it was the cheapest at 1.80 x 10^-4 mol per cent. Post Lab Questions: 1) Based only on your (and your classmates) results, which antacid will you take if needed? Why?  I would take Alka-Seltzer from group 3 because it is the cheapest and has the most mass effectiveness making it a very reliable antacid. 2) How many grams of acid will be neutralized by a Maalox antacid tablet that contains 0.350 g of CaCO3?  CaCO3 + 2HCl- CaCl2 + H2O + CO2  (0.350 grams of CaCO3)/ (100 grams) = 0.0035 moles of CaCO3  0.0035 moles of CaCO3 * 2 moles of HCl= 0.007 moles of HCl. 3) If you want to increase the pH of the stomach from 1 to 2 using an antacid tablet, how many grams of CaCO3 will be required to change the pH value? Assume stomach acid is HCl, and you have a stomach volume of 1 L.  CaCO3 + 2HCl  CaCl2 + H2O + CO2  A pH value of 1 would give us a concentration of 0.1 M HCl. When the pH value is 2, the concentration will go off from 0.1 M to 0.01 M. As a result, we will then do 0.1-0.01= 0.09. Since the ratio ends up being a 1:2 ratio, we will then do 0.9/2 which will give us 0.45 moles of CaCO3 which will be required to change the pH value. Also, another thing to note is that 4.5 grams of CaCO3 is equivalent to 0.45 moles 4) Magnesium hydroxide, Mg (OH)2 is another active ingredient of some antacids. How does Mg (OH)2 work to relieve the pain caused by excess stomach acid? Write the equation for this acid-base neutralization reaction.  Mg (OH)2 + 2HCl- MgCl2 + H2O  Since Mg (OH)2 is a base it takes away the stomach pains which was cause by excess stomach acid (HCl) build up, HCl is an acid and Mg (OH)2 is a base.

5) An antacid tablet was dissolved in 26.00 mL of 0.650 M HCl. The excess acid was back titrated with exactly 11.44 mL of 1.05 M NaOH. The average weight of a tablet is 0.834 grams. The tablet came from a bottle of 150 tablets that cost $3.99. a) Calculate the moles of HCl neutralized by the tablet  26 mL= 0.026 L of HCl 11.44 mL= 0.01144 L of NaOH  (0.026 L) (0.650 M) = 0.0169 M HCl  (0.01144 L) (1.05 M) = 0.012012 M NaOH  0.0169 M HCl - 0.012012 M NaOH = 0.004888 M HCl is neutralized by the tablet b) Calculate the mass effectiveness of the antacid.  Mass Effectiveness= (0.004888 M HCl)/ (0.834 grams) = 0.0058609113 mol/gram c) Calculate the cost effectiveness of the antacid.  Price per tablet = ($3.99) (100 cents/ $1) (1 bottle/ 150 tablets) = 2.66 cents  Cost effectiveness = (0.004888 M)/ (2.66 cents) = 0.001837594 mol/cent...