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CHEM 104 Experiment 3 Titrations and titration

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Name: Date: Experiment #: 3 Title: Titrations and titration curves Purpose: The purpose of this to perform titration analyses, including neutralization titrations, which occur between an acid and a base. Procedure: After gathering the necessary supplies, it was decided that we would perform reactions between the following solutions: strong acid/strong base, weak acid/strong base and strong acid/weak base. Standardization titration of NaOH : Used a strong acid/weak base. We determine the molarity of the NaOH by titrating it against potassium hydrogen phthalate. The phenolphthalein indicator was added to the solution of NaOH in a beaker along with water. We expect the solution to change from colorless to pink. We then documented the total amount of NaOH added from the buret to establish the color change. KHC8H4O4 + NaOH NaKC8H4O4 + H2O Standardization titration of HCl : Used a strong acid/strong base. The starting color of the solution is a translucent light yellow. The indicator utilized in this experiment is bromothymol blue, which was added to a solution of HCl. The given molarity of NaOH is 0.130M. Our goal endpoint pH was ~7.0. The goal color change is yellow to blue. HCl + NaOH NaCl + H2O Standardization titration of vinegar : Used weak acid/strong base. For this experiment, we utilized weak acid vinegar & strong base NaOH. After obtaining 3.09 g of vinegar, we added the NaOH indicator via the buret until a pink color change was obtained. A total of 19.7 mL of NaOH was added. HC2H3O2 + NaOH NaC2H3O2 + H2O Standardization titration of ammonia: After obtaining a graduated cylinder, scale, & household ammonia, a beaker was placed on a scale & zeroed. Ammonia drops were then added to a total of 2.0693 g. Methyl orange indicator (orange in color means neutral or more leaning towards neutral) added to the ammonia solution (which is a base). The goal is to change the color from yellow back to orange. NH3 + HCl NH4 + Cl Standardization titration of antacid tablets : After obtaining a generic brand of antacid tablets

Chemistry Notebook (base), we selected a few yellow-colored tablets & crushed them using a mortar & pestle. HCl was added to the base & we then planned on back-titrating. Next, we added 25.0 mL of 0. M

Chemistry Notebook HCl using a pipet to a flask of crushed antacids. Next, we boiled this solution, which is supposed to burn off any carbonic acid. Lastly, bromophenol blue was added back to the solution using a buret until the solution was a purplish/blue (indicating a pH of 3.0 – 4.6). Standardization titration using pH meter: For this last experiment, we performed a titration curve. First, we obtained a weak acetic acid and mixed with NaOH (strong base). When adding, we obtained pH measurements & correlating volume measurements (approx. 0.5-1 mL at a time). This was done via a pH meter. Data/Results/Calculations: Standardization titration of NaOH: Total NaOH added: 19.2 mL Mass of KHC8H4O4: 0.51g Volume of NaOH: 19.2 mL Molecular Weight (MW)=

NaOH Molarity: [0.51g / 204.2 g/mol] / [19.2ml/1000 mL/L] = 0.130M Standardization titration of HCl: Total NaOH added: 21. mL Volume of HCl: 25.0 mL Volume of NaOH: 21.9 mL Molarity of NaOH: 0.130 M HCl Molarity x (25.0 mL / 1000) x (1 / 1) = 0.130 x (21.9 mL /1000) = 0.114 M Standardization titration of vinegar: Total NaOH added: 19. mL. Mass of vinegar: 3.09 g Volume of NaOH: 19.7 mL Molarity of NaOH: 0.130M Molecular weight (MW): 60. % of HC2H3O2 = [(19.7/1000) x 0.130 x 60.052 x 100] / 3.09 = 4.95% Standardization titration of ammonia: Total mass of ammonia: 2.069 g Total HCl added: 25.2 mL of 0.106 M HCl HCl: 0.106 M Molecular Weight (MW): 17. % ammonia in household ammonia = [(25.2/1000) x 0.106 x 17.034 x 100]/2.0693 = 2.20% Standardization titration of antacid tablets:

Chemistry Notebook Total mass of antacid: 0.2148 g Total NaOH added: 2.9 mL of 0.107 M NaOH Molar weight (MW): 100. Volume of HCl: 25.0 mL of 0.106 M HCl Volume of NaOH: 3.9 mL of 0.107 M NaOH Excess HCl added: (0.106 M x 25.0 mL)/1000 = 0. Moles of base = (0.107 M x 3.9 mL) / 1000 = 0. HCl to neutralize CaCO3 = 0.00265 – 0.0004173 = 0. moles Moles of CaCO3 = 0.0022327 moles / 2 = 0.00111635 moles Mass (g) of CaCO3 = 0.000111635 moles x 100.09 = 0.1117 g % of CaCO3 = (0.1117 g x 100) / 0.2148 g sample = 52% Standardization titration using pH meter: 1 mL = 3.06 pH (no NaOH added yet) 2 mL = 3.35 pH (with added base) 3 mL = 3.54 pH 4 mL = 3.67 pH 5 mL = 3.84 pH 6 mL = 4.08 pH 7 mL = 4.16 pH 8 mL = 4.27 pH 10 mL = 4.41 pH 11 mL = 4.48 pH 12 mL = 4.56 pH 13 mL = 4.63 pH 14 mL = 4.77 pH 15 mL = 4.78 pH 22 mL = 5.46 pH 22.5 mL = 5.57 pH 23 mL = 5.69 pH 23.5 mL = 5.83 pH 24 mL = 6.03 pH 24.2 mL = 6.16 pH 24.5 mL = 6.37 pH 24.8 mL = 6.82 pH 24.9 mL = 7.36 pH 25 mL = 8.37 pH (We see a firm color change to pink) 25.2 mL = 9.15 pH 25.3 mL = 9.74 pH 25.5 L = 10.11 pH 25.7 mL = 10.42 pH 26.1 = 10.69 pH 26.8 mL = 11.01 pH

Chemistry Notebook 27.4 mL = 11.16 pH 28 mL = 11.25 pH 29 mL = 11.39 pH 30 mL = 11.50 pH 31 mL = 11.58 pH 32 mL = 11.64 pH 33 mL = 11.69 pH 34 mL = 11.74 pH 35 mL = 11.79 pH (curve has now leveled off & this is a rich pink in color) pH color change occurred between 8.0 & 9. Half-neutralization volume = 12.5 mL – when we saw a firm color change Pka = - log ka = 4. Since -log ka = 4.60 then log Ka = -4. Antilog (log ka) = antilog (-4.60) Ka = 2.51 x 10 - Conclusions: Several standardizations of titration were performed between acid & base solutions. In doing so, we were able to calculate molarity, % of solutions, & evaluate the titration curve for a given experiment. Notes: Titration – common lab method of quantitative volumetric analysis that is used to determine the unknown concentration of a substance by addition of an exactly measured volume of solution of a reacting substance of known concentration

• Measured additions of one chemical to another, in which the 2 react
• Weak base, weak acid
• Strong acid, strong base In order to perform a titration, we must have an unknown material (we don’t know the concentration) and a known material.