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Acid/Base Titration , Lab Questions powered by Mettler Toledo.
Typology: Lab Reports
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Workshop 1 1 Powered by METTLER TOLEDO
Vinegar is typically made from the fermentation of alcoholic liquids such as wine. Its main constituents are water and acetic acid, usually about 5 %. The acid in vinegar is produced by bacteria, which convert ethanol to acetic acid. An easy and accurate way to determine the acetic acid content is the direct titration with sodium hydroxide (NaOH).
Sodium hydroxide is corrosive! Skin and especially eye contact must be avoided. Always wear a lab coat, gloves and protective goggles during this workshop.
titration standard. For this purpose accurately weight 0.08 – 0.12 g of potassium hydrogen phthalate into a titration beaker and add 50 mL of deionized water. If you use an indicator add a small amount of phenolphthalein solution (0.1 % in ethanol) to the solution. Start the titration by adding small amounts of titrant (manual titration) or by starting the automated titration, and stir during the whole titration. Titrate until the color changes from colorless to pink (manual titration) or until the EQP is recognized by the automatic titrator. Calculate the titer from the used volume. Rinse the electrode and dispensing tubes with deionized water between every measurement (only for automated titration).
C 7 H 4 KO2-COOH + NaOH C 7 H 5 O2-COOK + H 2 O std. substance titrant reaction products 204.23 g/mol 40.00 g/mol
CH 3 COOH + NaOH CH 3 COONa + H 2 O analyte titrant reaction products 60.05 g/mol 40.00 g/mol
Workshop 1 2 Powered by METTLER TOLEDO
Determine the titer at least three times and calculate the mean value, standard
Determine the acetic acid content in a vinegar sample. Accurately weight about 1 g of vinegar in a titration beaker and add 50 mL of deionized water. To perform the titration, follow the same procedure as for the titer determination.
Determine the acetic acid content (in %) at least three times and calculate the mean value and standard deviation.
Neutralize (pH 7) the aqueous solutions before final disposal.
Calculation:
g/mol) 10: Factor for mg to g and % conversion (in mg/(g·%))
Expected result:
The titer should be around 1 for a fresh titrant solution.
Calculation:
10: Factor for mg to g and % conversion (in mg/(g·%))
Expected result:
The acetic acid content in vinegar is usually around 5 %.
Three titer determinations were performed using KHP with a purity of 99.8 %. In the
1 0.087 g 4.265 mL 0. 2 0.092 g 4.501 mL 0. 3 0.105 g 5.135 mL 0.
The titer of the first measurement was calculated as follows:
204.23 (^) molg
10
mg g·% ∙ 99.8 % ∙
g mmol
0.087 g
4.265 mL∙ 0.1 molL ∙ 0.2046 (^4) mmolg
Mean: 0.
After the titer determination three measurements of a vinegar sample were performed. For these three measurements the following sample amounts were used and the following results were obtained:
1 0.982 g 7.165 mL 4.37 % 2 0.881 g 6.463 mL 4.40 % 3 0.912 g 6.686 mL 4.39 %
The calculation of the first measurement is shown here in detail:
g mol 10
mg g·% ∙ 1
g∙% mmol
7.165 mL ∙ 0.
mol L ∙^ 0.9983 ∙^ 6.^
g∙% mmol