acid base titration anaylsis

8/10/2019 Acid Base Titration Anaylsis

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: 07-07-14

ABSTRACT

In this experiment, we learned the technique of acid-base titrations and compared the efficiency

of commercially available antacids by looking at their weight of HCl/wt. of antacid values. Two antacid

tablets were crushed, dissolved in 50.0mL 0.1M HCl; indicators were placed, titrated with 0.1M NaOH and

calculation of the weight of HCl that reacted with the 1g of antacid tablet was done after two trials. The

weight of HCl that reacted with the tablet is calculated and noted as well as compare the efficiency of the

commercially available antacids by looking at their HCl/wt of antacid values. All methods used in the

experiment was effective in learning the technique of acid-base titrations and comparing the efficiency ofantacids by looking at the HCl/wt of antacid values.

INTRODUCTION

Antacidsare substances that neutralize stomach acidity and one of the most widely used self-prescribed medicines. They are basic in nature. They are taken to relieve medically undefined conditionssuch as heartburn, acid indigestion and sour stomach. Excessive hydrochloric acid in the stomach causesa feeling of discomfort and a burning sensation beneath the breastbone resulting from a spastic backflowof this acid content into the esophagus.

Antacid tablets counteract stomach acidity by reacting with the excess hydrochloric acid in thestomach. Some of these tablets contains Al(OH)3or Mg(OH)2or both, while some contain CaCO3. Thesecomponents neutralize the acids. Here are some known brands in the Philippines are: Maalox, Alka-Seltzer, and Gaviscon.

The efficiency of the antacid tablet may be determined and compared by finding the number of gramsof HCl that can be neutralized by 1g of the tablet. The higher the amount of HCl that can be neutralizedby the 1g tablet, the more efficient the antacid is. The volume of unreacted HCl in the antacid mixture istitrated with NaOH to determine the efficiency of an antacid tablet.

The chemical equation that describes the reaction between the HCl and the NaOH:

The equation used to calculate the amount of HCl neutralized is:

Since both HCl and NaOH have 1 equivalence point per mole, the following equation may also beused:

Experiment no. 11:

Acid-Base Titrations: Analysis of Antacid

Tablets

Guillermo, Janina Suzette C.Escudero, Angela Julia R.

De La Salle UniversityDasmariasDasmarias, Cavite Philippines


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MATERIALS AND METHODS

The experiment on Acid-Base titrations primarily used reagents that are either strong acid or

strong base to greater facilitate the effect and function of titration. In to our experiment we have used two

antacid tablets with its generic name sanofiaventis. The tablets were crushed separately using a mortar

and pestle. They were also weighed separately using the analytical balance. For accuracy of results, we

have placed each one of them in a paper box made up of one sheet of paper. After getting their actual

weight, they are placed in separate in different Erlenmeyer flasks to conduct at least 2 trials of the

experiment. After placing the crushed tablets in the flask, we added 50.0 mL of 0.1 M of HCl to theantacid tablets and we let it dissolve. Continuous mixture is a must while performing the experiment to

obtain faster results. Then we added 2 drops of phenolphthalein indicator using a medicine dropper into

the mixture for us to see if the mixture has been neutralized already or not. Next we prepare the titration

set up by using a base burette with a burette clamp attached to the iron stand. We placed at unknown

volume of NaOH to the burette but not the flask with the antacid and HCl mixture. Place the flask under

the burettes opening and fill the flask with enough NaOH until the mixture turns into faint pink color. This

procedure will be repeated for the second antacid tablet placed in the other Erlenmeyer flask. After

reacting, calculate the weight of HCl that reacted with the antacid tablet by using the formula.

Formula for calculating the weight of HCl:

of HCl = MWHCl [ (Vol. in literHCl) (molarityHCl)

(Vol. in literNaOH) (molarityNaOH)

RESULTS AND DISCUSSION

Table 1: Analysis of Acid-Base titration using Antacid tablets

Antacid tablets (1 & 2): Sanofiaventis

No. of trials 1 2

Weight of the tablet 0.5877 g 0.5830 g

Final volume of NaOH used 38.2 mL 31.1 mL

Initial volume of NaOH 0 mL 0 mL

Volume of NaOH used 38.2 mL 31.1 mL

Molarity of NaOH 0.1 M 0.1 M

Molarity of HCl 0.1 M 0.1 M

Volume of HCl 50 mL 50 mL

Weight of HCl that has reacted

With the antacid table 0.043 g 0.069 g

Weight of HCl / gram of antacid tablet 0.0732 0.1184

Using antacids tablets facilitated the acid-base titration experiment. The generic name of theantacid tablet was Sanofiaventis, white in color and made up of Ca(OH)2and Mg(OH)2which areconsidered to be bases because of the presence of hydroxides. We divide the experiment into two trialsat least to compare which of the antacid tablet has more efficiency. For the first trial, the initial weight ofthe antacid tablet itself is 0.5877g. We dissolved it in a 50mL 0.1 M of HCl, which is considered as astrong acid.At first, the neutralization reaction wasnt obvious because the moles of the antacid were notenough to react with the moles hydrochloric acid to facilitate neutralization. Before proceeding to titration,we have used the phenolphthalein indicator of at least 2-3 drops in the mixture to indicate if we already


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obtain the equivalence point of the mixture. The phenolphthalein indicator uses a faint pink color as a signof equivalence point within mixtures. Next, we have placed unknown amount of NaOH, with the samemolarity of 0.1 to the base burette and titrate the mixture by obtaining enough amount of the NaOH untilthe mixture appears into faint to light pink color solution. As to result of our experiment for the first trial,from an initial volume of NaOH of 0mL to a final volume of 38.2 mL. Same procedure and reagents wasused for the second trial but the outcomes are different.

For the second trial of the experiment, the weight of the antacid tablet was 0.5830 grams, againdissolved in a 50mL 0.1 M of HCl. We still placed 2 drops of phenolphthalein indicator in the mixture andagain titrate the mixture with an unknown amount of NaOH still with a 0.1 Molarity. From an initial volumeof 0 mL, we have come up with a final volume of 31.1 mL NaOH until the solution turns into faint pinkcolor which is an indication of neutralization.

After obtaining the equivalence point of both antacid tablets done in separate trials, we nowcomputed for the weight of HCl that has reacted with the antacid tablet. This can be calculated by usingthe formula. of HCl = MWHCl [ (Vol. in literHCl) (molarityHCl) (Vol. in literNaOH) (molarityNaOH),whereas the calculated Molecular weight of HCl is 36.46 g/mol. For the first trial, by using the data given,we have obtain that 0.043 g of HCl reacted with the antacid tablets. In comparison with the second trial,the weight of HCl that has reacted with the antacid table is 0.069 grams. And to compute for the efficiencyof the antacid tablet, we divided the weight of the HCl by the grams of the antacid tablet. For the first trial,the result was 0.0732 and for the second trial 0.1184. This means that in terms of greater effect, thesecond tablet of antacid was better because in the first place as to the results of the experiment, it onlyuses 31.1 mL of NaOH to titrate the mixture and the resulting efficiency of the neutralization effect was of

greater amount in comparison with the first tablet.

REFERENCES

(1) Samonte J.L, Figueroa L.V General Chemistry Laboratory Manual 4th Edition, C&E Publishing Inc.,

2014.

(2) Chang R., Chemistry. 6thEdition NY: WBC Mc Graw Hill, 1996

(3) Zumdahl, S. S. (1997). Chemistry, (4thEdition) Boston, NY: Houghton Mifflin Company.

acid base titration anaylsis

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