Experiment 3 NEUTRALIZATION CAPACITY OF COMMERCIAL ANTACID TABLET PDF

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LAB REPORT OF NEUTRALIZATION CAPACITY OF
COMMERCIAL ANTACID TABLET...

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UNIVERSITI TEKNOLOGI MARA

FACULTY OF APPLIED SCIENCES BACHELOR OF SCIENCE (HONS.) APPLIED CHEMISTRY

CHEMICAL LABORATORY

COURSE EXPERIMENT NUM EXPERIMENT

: ANALYTICAL CHEMISTRY (CHM421) : EXPERIMENT 3 : NEUTRALIZATION CAPACITY OF COMMERCIAL ANTACID TABLET

NAME

: MIMI ATHIRAH BT R AZIMI

MATRIC NUM

: 2020897434

GROUP

: AS2451M3 LAB421

DATE OF SUMMISION

: 12 NOVEMBER 2020

DATE OF EXPERIMENT

: 29 OCTOBER 2020

LECTURER’S NAME

: DR NURULFAZLINA EDAYAH RASOL

EXPERIMENT TITLE Neutralization Capacity of commercial antacid tablet

ABSTRACT This experiment was conducted to prepare the hydrochloric acid solution, standardise the acid against sodium hydroxide and to determine neutralization capacity of a commercial antacid tablet. In this experiment for part A, 250 ml of 0.5 M HCl was prepared by diluting 20.83 ml of 6.0 M HCl. Then, the standard NaOH solution from previous experiment was used for standardisation of acid against NaOH and determination of neutralisation capacity of an Antacid Tablet. The antacid tablet was crush and dissolved in excess amount of standard acid with known concentration and standardised with standard NaOH to identify the amount of excess acid. Back titration method was performed in this experiment. The neutralization capacity of antacid tablet is 1.6425 x 10-3mol g-1. The percentage error obtained from the experiment’s calculation is 33.3 %.

OBJECTIVES 1. To prepare Hydrochloric acid solution. 2. To standardize the acid against Sodium Hydroxide. 3. To determine the Neutralization Capacity of a Commercial Antacid Tablet. INTRODUCTION In this experiment, the preparation of an approximately concentration of hydrochloric acid (HCl) solution and standardisation of it against standard sodium hydroxide solution (NaOH) was done in Part A and Part B. Hydrochloric acid was vaporises rapidly in room temperature since it is not a primary standard. The hydrochloric acid referred as a tertiary standard solution when the accurate molarity of hydrochloric acid was obtained. The carbonate ion (CO32-) or hydroxide ion (OH-) is normally use in antacid tablet as it is the active ingredient. These all work by neutralizing acid in the stomach. They tend to work quickly to relieve heartburn. Most of the antacid tablet are not dissolved in water alone as it need to dissolve the antacid tablet in HCl solution first. The determination of mass of hydroxide ion (OH-) and percentage of it that is present in the tablet and the neutralising capacity of the tablet which is the amount of HCl that it can neutralise was the main purpose of this experiment. Below is the equation that involved in this experiment:𝐻𝐶𝑙 (𝑎𝑞) + 𝑁𝑎𝑂𝐻 (𝑎𝑞) → 𝑁𝑎𝐶𝑙 (𝑎𝑞) + 𝐻2 𝑂 (𝑙) 𝐴𝑙 (𝑂𝐻)3 → 𝐴𝑙 + 3𝑂𝐻− 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 needed to prepare 250 ml of 0.5M acid was calculated and 80% of distilled water required was poured into a 500 ml conical flask. The previous amount of 6.0M HCl volume was obtained by using a measuring cylinder and the volume then was transferred into the flask. Distilled water was added again until 250 ml mark on the conical flask. The flask was covered nicely with a parafilm and the solution was mixed perfectly. The solution was properly labelled. B. Standardisation of The Acid Against Sodium Hydroxide The standard solution of NaOH from previous experiment was used to standardise the HCl solution to form tertiary standard 50 ml burette was rinsed and filled with NaOH solution. The initial reading was recorded right away after checking and removing the air bubbles at the burette’s tips. Second step, 10 mL of prepared HCl solution were accurately pipetted and transferred into a clean conical flask. 20 ml of distilled water was added into a flask followed by 3 drops of phenolphthalein indicator. The solution then was titrated with NaOH solution and the final volume reading of the titrant also was taken. The experiment was repeated once again. C. Determination of Neutralization Capacity of An Antacid Tablet The burette that containing NaOH solution above was refilled and the initial volume reading was recorded again. Next, one antacid tablet provided in the laboratory was obtained. The tablet was weighed and the mass was recorded without touching the tablet with hands. The antacid tablet was crushed by using a mortar and pestle. The crush tablet was then split into two samples of about similar weight. Each sample was reweighed to the nearest milligram and the mass of each crushed sample was recorded. Then each sample was transferred to a clean 250 mL conical flasks. 250ml of distilled water was measured approximately and poured into a flask. A 25 ml of standard acid was accurately dispensed using a volumetric pipette into the flask containing the crushed tablet. The contents were heated in the flask by a Bunsen burner the solution was boiled for 5 minutes. Lastly, the solution was let to cool down to room temperature by carefully placing the flask under running of tap water. Five drops of methyl orange indicator were added to the solution. The indicator changed colour from red (acid) to orange (base).The titration was ensured to be careful as the endpoint may not be very obvious. A back titration was done with the standard HCl. A measured volume of standard HCl was carefully added to return to the red colour solution and then the solution was titrated again to the endpoint using

standard base. The experiment was repeated with the other one samples and all the data was recorded in lab notebook. DATA/RESULTS AND CALCULATION A. Preparation of The Hydrochloric Acid (HCl) Solution. M1 = 0.6M V1 = ? M2 = 0.5M V2 = 250 ml M 1V 1 = M 2V 2 (0.6)V1 = (0.5)(250) V1 = (0.5)(250) / 0.6 = 20.83 ml B. Standardisation of The Acid Against Sodium Hydroxide NaOH Volume of the acid used (ml) Final reading of NaOH Initial Reading NaOH Volume of NaOH used (ml)

1 10.0

2 10.0

36.0 6.0 30.0

43.1 13.1 30.0

MAVA = MBVB MA = ? , VA = 10.0ml and MB = 0.2 M , VB = 30.0ml MA (10.0) = (0.2)(30.0) MA = (0.2)(30.0) / (10.0) = 0.6M HCl

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

Weight of crushed antacid tablet (g) Volume of standard HCl added (ml) Volume of standard NaOH (ml), First titration

1 0.2926

2 0.2895

20.0

20.0

46.80

36.80

Volume of standard NaOH (ml), Second titration Vol of standard NaOH used (ml)

10.80

20.60

57.60

57.40

𝐻𝐶𝑙 (𝑎𝑞) + 𝑁𝑎𝑂𝐻 (𝑎𝑞) → 𝑁𝑎𝐶𝑙 (𝑎𝑞) + 𝐻2 𝑂 (𝑙) 𝐴𝑙(𝑂𝐻)3 (𝑠) → 𝐴𝑙 + 3𝑂𝐻− 𝐴𝑙(𝑂𝐻)3 (𝑠) + 3𝐻𝐶𝑙 (𝑎𝑞) → 𝐴𝑙 𝐶𝑙3 (𝑎𝑞) + 3𝐻2 𝑂 (𝑙) 1. n (HCl) = MV M = 0.6M V = 0.02L Mol HCl = (0.6) x (0.02) = 0.012 mole 2. no of excess HCl = MNAOHVNAOH 𝑓𝑖𝑟𝑠𝑡 𝑡𝑖𝑡𝑟𝑎𝑡𝑖𝑜𝑛 (𝑓𝑖𝑛𝑎𝑙) =

(0.2 𝑥 57.60) = 0.01152 𝑚𝑜𝑙𝑒 1000

𝑠𝑒𝑐𝑜𝑛𝑑 𝑡𝑖𝑡𝑟𝑎𝑡𝑖𝑜𝑛 (𝑓𝑖𝑛𝑎𝑙) =

0.2 𝑥 57.40 = 0.01148 𝑚𝑜𝑙𝑒 1000

3. Mol of HCl reacted with NaOH = mol of HCl – mol of excess HCl 𝑚𝑜𝑙 𝑜𝑓 𝐻𝐶𝑙 𝑟𝑒𝑎𝑐𝑡𝑒𝑑 (𝑓𝑖𝑟𝑠𝑡 𝑡𝑖𝑡𝑟𝑎𝑡𝑖𝑜𝑛) = 0.012 𝑚𝑜𝑙 − 0.01152 𝑚𝑜𝑙 = 4.8 𝑥 10−4𝑚𝑜𝑙 𝑚𝑜𝑙 𝑜𝑓 𝐻𝐶𝑙 𝑟𝑒𝑎𝑐𝑡𝑒𝑑 (𝑠𝑒𝑐 𝑡𝑖𝑡𝑟𝑎𝑡𝑖𝑜𝑛) = 0.012 𝑚𝑜𝑙 − 0.01148 𝑚𝑜𝑙 = 5.2 𝑥 10−4𝑚𝑜𝑙 𝑇𝑜𝑡𝑎𝑙 𝐻𝐶𝑙 𝑚𝑜𝑙 𝑟𝑒𝑎𝑐𝑡𝑒𝑑 𝑤𝑖𝑡ℎ 𝑎𝑛𝑡𝑎𝑐𝑖𝑑 𝑡𝑎𝑏𝑙𝑒𝑡 = (4.8 𝑥 10−4 ) + (5.2 𝑥 10−4) = 1 𝑥 10−3 𝑚𝑜𝑙𝑒 4. 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑎𝑛𝑡𝑎𝑐𝑖𝑑 𝑡𝑎𝑏𝑙𝑒𝑡 = 𝑚𝑜𝑙 𝑥 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 = (1 𝑥 10−3)𝑥 78𝑔/𝑚𝑜𝑙 = 0.078 𝑔 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 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 0.6088𝑔

= 1.64 𝑥 10−3 𝑚𝑜𝑙𝑔−1 8. The percentage of Al(OH)3 in 1 tablet 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑜𝑓 𝐴𝑙(𝑂𝐻)3 𝑖𝑛 1 𝑡𝑎𝑏𝑙𝑒𝑡 =

0.025974𝑔 𝑥 100 0.078𝑔

= 33.3%

DISCUSSION

This experiment was carried out to determine the neutralization capacity of a commercial antacid tablet. Preparation of hydrochloric acid solution and the standardization of the acid against sodium hydroxide (NaOH) was involved in this experiment in order to determine neutralization capacity of a commercial antacid tablet. The method that has been used in this experiment is back titration method, this method was performed to obtain the third objective. A back-titration method is used when the molar concentration of an excess reactant is known. This method was used for the determination of analyte concentration reacted with a known amount excess reagent. Next, the remaining excess was titrated with a second reagent. For Part A the preparation of 250 ml of 0.5 M HCl needed 20.83 ml from 6.0 M HCl. The volume of 6.0 M HCl needed was obtained by using a dilution formula. Then, for part B, the standardisation of HCl against NaOH obtained 30 ml for both first and second titration. The molarity of acid used in this experiment is 0.6M after calculated. For part C, the neutralization of capacity of commercial antacid tablet was determined by using back titration method. The antacid tablet was crushed and heated with standard acid solution also followed by titration with NaOH solution. The mass of Al(OH)3 in 1 tablet obtained was 0.025974 g. The neutralization capacity of commercial antacid tablet was 1.64 x 10-3 mol/g. There might be some error occurred while doing the experiment process which can affect the result exactness. Several factors can cause errors in titration findings, including misreading volumes, mistaken concentration values or faulty technique. Care must be taken as the solution of the known

concentration is introduced into a specific volume of the unknown through laboratory glassware such as a burette or pipette. Not to forget, the cleanliness of the apparatus was not fully cleaned and not fully dried can also affect the readings. For example, the air bubble that was still trapped and not fully remove will affect the reading of the sample. The position of eye was not perpendicular with the reading scale which can cause the parallax error. Other than that, the misreading value of the actual mass sample while using the electronic balance also can lead to a slightly different in value as the contamination from other sources might take place in the readings. To prevent this from happening, analytical balances should be placed in a protected environment away from temperature extremes such as direct sunlight, heating and AC vents.

CONCLUSION All in all, the 3 main objectives of the experiment which is to prepared HCl solution, to standardise the acid against sodium hydroxide and to determine the neutralization capacity of a commercial antacid tablet were successfully performed. The mass and percentages of Al(OH)3 in 1 tablet obtained were 0.025974 g and the neutralization capacity of commercial antacid tablet was 1.64 × 10-3 .The percentage of Al(OH)3 in 1 tablet is 33.3%.

REFERENCES 1. Anne Marie Helmenstine, P. (2019, October 7). What is Back Titration. Retrieved 15 November 2020, from https://www.thoughtco.com/back-titration-definition-608731

2. Kohn, R (2020, September 11). How to Avoid Analytical Balance Weighing Errors. Retrieved 14 November 2020, from https://www.tovatech.com/blog/15006/digital-scales/how-to-avoid-analyticalbalance-errors

3. UC CEAS .(2020). Acid Neutralizing Capacity of an Antacid. Retrieved from https://ceas.uc.edu/content/dam/ceas/documents/CEEMS/instructionalunits/NaturalAntacids_CB/Acid %20neutralizing%20capacity%20of%20an%20antacid.docx#:~:text=Background,which%20aids%20i n%20food%20digestion.&text=Commercial%20antacids%20containing%20one%20or,acid%20that% 20it%20can%20neutralize. 4. Knott, D. (2020, April 14). Antacids: How do antacids work? Retrieved November 14, 2020, from https://patient.info/digestive-health/indigestion-medication/antacids 5. Senese, F. (2010). Why is acid always added to water, and not the reverse? Retrievedfrom https://antoine.frostburg.edu/chem/senese/101/safety/faq/always-add-acid.shtml

QUESTION

1. Acid is always added to water, and never the reverse. Why? A large amount of heat is released when strong acids are mixed with water. The solution forms will be very dilute and the small amount of heat released is not enough to vaporize and spatter it but if water was added to acid, an extremely concentrated solution of acid will be form. So much heat is released that the solution may boil very violently, splashing concentrated acid 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) → 𝐴𝑙 𝐶𝑙3 (𝑎𝑞) + 3𝐻2 𝑂 (𝑙) 3. Write a balanced chemical equation for the reaction if the antacid contains carbonate ion. CaCO3(s) + 2 HCl(aq) -----> CaCl2(aq) + H2O(l) + CO2(g)...