Experiment 3 CHM421 Online Lab Report PDF

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nullLABORATORY REPORTCHM(ANALYTICAL CHEMISTRY)NAME: ‘AINA SUFI BINTI HAMDANSTUDENT NO.: 2020575445GROUP: AS2465BEXPERIMENT NO: 3EXPERIMENT TITLE.: NEUTRALIZATION CAPACITY OF COMMERCIAL ANTACID TABLETDATE OF EXPERIMENT: 25TH OCTOBER 2021DATE OF REPORT SUBMISSION: 30TH OCTOBER 2021NAME OF LECTURER: DR...

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Experiment 3 CHM421 Online Lab Report Organic Chemistry (CHM412)

LABORATORY REPORT CHM421 (ANALYTICAL CHEMISTRY)

NAME: ‘AINA SUFI BINTI HAMDAN STUDENT NO.: 2020575445 GROUP: AS2465B2 EXPERIMENT NO: 3 EXPERIMENT TITLE.: NEUTRALIZATION CAPACITY OF COMMERCIAL ANTACID TABLET DATE OF EXPERIMENT: 25TH OCTOBER 2021 DATE OF REPORT SUBMISSION: 30TH OCTOBER 2021 NAME OF LECTURER: DR NUR SOFIAH BINTI ABU KASSIM

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ABSTRACT This experiment was done in order to achieve the objective of this experiment which are to produce the hydrochloric acid solution, to systematize the acid against sodium hydroxide and to control the neutralization capacity of a commercial antacid tablet. In part A of this experiment, 20.83mL of 6.0M HCl was diluted in order to prepare a 250mL of 0.5M of HCl. Then, the standardization of acid against NaOH and the determination of neutralization capacity of an antacid tablet was performed using the standard NaOH solution from the previous experiment. In identifying the amount of excess acid, the antacid tablet was crushed and it is dissolved in the excess of standard acid with known concentration and it is standardized with standard NaOH solution. This experiment was done by applying back titration method throughout the process. The neutralization capacity of the antacid tablet obtain and the percentage error obtained from the calculation involved in this experiment are 1.64 x 10-3 mol/g and 33.3% respectively.

OBJECTIVES 1. To produce the hydrochloric acid solution. 2. To systematize the acid against sodium hydroxide. 3. To control the neutralization capacity of a commercial antacid tablet.

INTRODUCTION The preparation of the hydrochloric acid (HCl) solution with approximate concentration and the standardization of it against sodium hydroxide solution (NaOH) was completed in Part A and B of this experiment. The hydrochloric acid was mentioned as one of the tertiary standard solution when the molarity of HCl is obtained accurately. HCl is not a primary standard solution, hence it vaporizes rapidly when in room temperature. The active ingredient that is usually used in antacid tablet is the hydroxide ion (OH-) or the carbonate ion (CO32- ) which the antacid tablet works by neutralizing the acid in the stomach when it is consumed by a human being. It is normally known as the reliever of heartburn as it help to relieves the heartburn quickly. The antacid tablets are mostly cannot be dissolved in the water by itself but it needs to be dissolved in the HCl solution beforehand. Thus, the main purpose of this experiment was to determine the mass and the percentage of hydroxide ion as well as the neutralizing capacity of the tablet which is the amount of HCl.

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The equation involved in this experiment is stated below: HCl (aq) + NaOH (aq)

NaCl (aq) + H2) Al + 3OH-

Al(OH)3 Al(OH)3 (s) + 3HCl (aq)

AlCl3 (aq) + 3H2O (l)

METHOD A. Preparation of The Hydrochloric Acid (HCl) Solution The volume of 6.0M HCl is calculated to prepare 250mL of 0.5M HCl. The rough volume of distilled water required is also calculated. About 80% of the required distilled water is poured into a 500mL conical flask. The calculated amount of 6.0M HCl is obtained using a measuring cylinder and the volume is transferred into the flask. Distilled water is added to the 250mL mark on the conical flask. The flask is carefully covered with Parafilm and the solution is mixed well. The solution is labelled properly. B. Standardization of the Acid against Sodium Hydroxide In this procedure the secondary standard NaOH solution (from Experiment 1) will be used to standardize the HCl solution above to form a tertiary solution 1. A 50mL burette is rinsed and filled with the standard NaOH solution. The initial reading is recorded after checking and removing the air bubbles at the burette’s tip. 2. Pipette accurately and 10.0mL of the prepared hydrochloric acid solution is transferred into a clean conical flask. About 20mL of distilled water is added by 3 drops of phenolphthalein indicator to the flask and titrated to the end-point with the standard NaOH solution. The final volume of the titrant is recorded. This titration is repeated at least two more times. C. Determination of Neutralization Capacity of an Antacid Tablet 1. The above burette containing the NaOH solution is refilled. Any air bubbles present at the tip is checked and removed. The initial volume is recorded. 2. One antacid tablet provided in the laboratory is obtained. Without touching the tablet with your hands, the tablet is weighed and its mass is recorded. Carefully, the antacid tablet is crushed using a mortar and pestle. The crush tablet is split into two or three samples (depending on the weight of the whole tablet) of about similar weights. Each sample is reweighed to the nearest milligram. The mass of each crushed sample is recorded. Each sample is transferred to clean 250mL conical flask.

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3. 25mL of distilled water is measure approximately and poured it to flask. Dispensed accurately and carefully of your standard acid into the flask containing the crushed tablet. Next, the contents in the flask is heated with Bunsen burner. The solution is boiled for 5 minutes. The sample may not completely dissolve during the process due to presence of “fillers”, but any base in the sample will have reacted with the excess HCl. The remaining acid solution is checked using litmus paper as the flask now only contain remaining acid solutions. Note: If the solution is not acidic, then accurately added 25.0mL of the standard acid and boiled again for another 5 minutes. 4. The solution is let to cool to room temperature by carefully placing the flask under running tap water. Alternatively immersed in the flask in a container of tap water. 5 drops of methyl orange indicator is added to the solution. The indicator changes color from red (acid) to orange (base). Be very careful with the titration because the end point may not be very obvious. If the base is added too much, it will need to be back-titrate with standard HCl. It will have to add a carefully measured volume of standard HCl to return to the red color. Then, titrated again to the end-point using the standard base. 5. The experiment is repeated with the other two samples. All data is recorded. Clean-up Any remaining solution is drained from the burette. The burette is washed with tap water. Then, the stopcock is left open, the inverted burette is returned to the burette clamp. Also, the pipette is washed and the rest of the glass wares used with tap water and returned them back at their storage place.

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DATA & RESULTS A. Preparation of the Hydrochloric Acid (HCl) solution. M1 = 6.0M V1 = x M2 = 0.5M V2 = 250mL

M1V1 = M2V2 (6.0M)V1 = (0.5M)(250mL) V1 = (0.5M)(250mL) / (6.0M) = 20.83mL B. Standardization of The Acid Against Sodium Hydroxide NaOH 1

2

10.00

10.00

Final reading of NaOH

36.00

43.10

Initial reading of NaOH

6.00

11.10

Volume of NaOH used (mL)

30.00

32.80

Volume of the acid used (mL)

M1V1 = M2V2 M1 = x V1 = 10mL M2 = 0.22M V2 = 30.00mL

(x)(10mL) = (0.22M)(30.0mL) x = 0.66M

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C. Determination of Neutralization Capacity of An Antacid Tablet Weight of 1 whole antacid tablet = 0.6088g

Weight of crushed antacid

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0.2926

0.2895

20.0

20.0

46.80

36.80

10.80

20.60

57.60

57.40

tablet (g) Volume of standard HCl added (ml) Volume of standard NaOH (mL) First titration Volume of standard NaOH (mL) Second titration Volume of standard NaOH used (mL)

1. N(HCl) = MV M = 0.6M V = 0.02L Mol HCl = (0.6)(0.02) = 0.012 mole

2. No of excess HCl = MbVb First titration = [(0.2)(57.60)] / 1000 = 0.01152 mole Second titration = [(0.20(57.40)) / 1000 = 0.01148 mole

3. Mol of HCl reacted with NaOH = mol of HCl – mol of excess HCl Mol of HCl on first titration = 0.012 mol – 0.01152 mol = 4.8 x 10-4 mol Mol of HCl on second titration = 0.012 mol – 0.01148 mol = 5.2 x 10-4 mol Sum of HCl mol reacted with antacid tablet = Mol of HCl on first titration + Mol of HCl on second titration = (4.8 x 10-4 mol) + (5.2 x 10-4 mol) = 1 x 10-3 mol.

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4. Weight of antacid tablet = mol x molar mass = (1 x 10-3) x 78g/mol = 0.078g 5. Al(OH)3

Al + 3OH-

1 mol of Al(OH)3 in 1 tablet = 3 mol OH- ions 3 mol of OH- = 1 x 10-3 mol OH- x [(1 mol (Al(OH)3)/(3 mol OH-)] = 3.33 x 10-4 mol Al(OH)3 in 1 tablet 6. Mass of Al(OH)3 = mol x molar mass = (3.33 x 10-4) x (78 g/mol) = 0.025974 g

7. Neutralization capacity of antacid tablet = mol HCl neutralization/mass of antacid tablet = (1 x 10-3 mol HCl)/(0.6088 g) = 1.64 x 10-3 mol/g

8. The percentage of Al(OH)3 in 1 tablet = [(0.025974 g)/(0.078 g)]/100 = 33.3%

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DISCUSSION The purpose of this experiment is to determine the neutralization capacity of a commercial antacid table and it is also involving in the preparation of hydrochloric acid solution and the standardization of the acid against sodium hydroxide (NaOH) as part of the process in determining the neutralization capacity of the commercial antacid tablet. The method used in running the experiment is back titration method. This method was used to control the analyte concentration reacted with the excess reagent. It also applied when the molar concentration of an excess reactant is known. The remaining excess is then titrated with the second reagent. In part A, for the preparation of 250mL of 0.5M HCl, 20.83mL is needed form 6.0M HCl. The volume needed can be obtained by using the dilution formula which is the M1V1 = M2V2. Meanwhile in part B, the standardization of hydrochloric acid against sodium hydroxide obtained 30.00mL and 32.80mL for the first and second titration respectively. The molarity acid obtained by calculation used in this titration is 0.66M. In part C where the neutralization of capacity commercial antacid tablet was determined by using back titration method, the antacid tablet was crushed and heated in a standard acid solution followed by the titration of sodium hydroxide (NaOH) solution. The mass of Al(OH)3 in 1 tablet obtained from the process was 0.025974g and the neutralization capacity of the commercial antacid tablet is 1.64 x 10-3 mol/g. Some error could happen while running the whole process of the experiment which may affect the results to be accurate. A few factors that can be the source in errors such as in faulty in titration technique, misreading the volumes and mistaken the concentration values of the solution. These errors can be avoided such as error in titration technique, several practices can be done before running the experiment to sharpen the skills in using the apparatus needed in titration process. As example, the air bubble trapped in the burette or pipette must be removed to get a more accurate result. Next is error in misreading the volumes. This is also known as parallax error. The eye of the reader should be perpendicular to the reading scale on the apparatus when taking the value of the volume. Other than that, the apparatus used is also must be in a good condition with no residues which also can affect the results. Last but not least, the misreading in taking the actual mass of the sample while using the electronic balance also can cause error in the value taken as the contamination from other sources might interrupt the readings. This can be prevented by

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placing the analytical balances in a protected environment and away from extreme temperatures such as heating, sunlight and air conditioner vents.

CONCLUSION To conclude, all of the objective stated which are to determine the hydrochloric solution, to standardize the acid against sodium hydroxide and to control the neutralization capacity of a commercial antacid tablet were performed successfully. The mass of Al(OH)3 obtained in 1 tablet was 0.025974g meanwhile the mass of the neutralization capacity of commercial antacid tablet was 1.64 x 10-3. The percentage obtained for Al(OH)3 was 33.3%

QUESTIONS 1. Acid is always added to water, and never the reverse. Why? > It is because the mixture of acid with water will release some heat. When water is added to acid, it will form an extremely concentrated solution of acid while acid is added to water, the solution will be in a diluted form and the small amount of heat released is small and do not spatter. Hence, a lot of heat is released if water is added into water and can cause the solution to spatter out of the container. 2. Write a balanced chemical equation for a reaction of the antacid with HCl of the antacid contains hydroxide ion. Al(OH)3 (s) + 3HCl (aq)

AlCl3 (aq) + 3H2O (l)

3. Write a balanced chemical equation for the reaction if the antacid contains carbonate ion. CaCO3 (s) + 2HCl (aq)

CaCl2 (aq) + H2O (l) + CO2 (g)

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REFERENCES 1. Anne Marie Helmenstine, P. D. (2019, October 7). What is back titration? ThoughtCo. Retrieved October 26, 2021, from https://www.thoughtco.com/back-titration-definition608731. 2. Asian Journal of Research in Medical and Pharmaceutical Sciences. (n.d.). https://doi.org/10.9734/ajrimps 3. Why is acid always added to water, and not the reverse? General Chemistry Online: FAQ: Laboratory operations: Why is acid always added to water, and not the reverse? (n.d.). Retrieved October 26, 2021, from https://antoine.frostburg.edu/chem/senese/101/safety/faq/always-add-acid.shtml. 4. Abdu, K., & Abbagana, M. (n.d.). Evaluation of neutralizing capacity of different commercial brands of antacid tablets. ChemSearch Journal. Retrieved October 26, 2021, from https://www.ajol.info/index.php/csj/article/view/130155. 5. Annotated lab report - write online. (n.d.). Retrieved October 26, 2021, from https://writeonline.ca/media/documents/LabReport-AnnotatedFull.pdf.

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