Historically, vinegar played an important role in the preservation of food becau

Question

Historically, vinegar played an important role in the preservation of food because of the acidity and antimicrobial properties of its main component, acetic acid. There are many types of vinegar found at your local grocery store, including balsamic, rice, red wine, and apple cider vinegars. A titration will help you determine the concentration of acetic acid (CH3COOH) in vinegar. The balanced equation for the titration of acetic acid in vinegar with sodium hydroxide (NaOH) is as follows.

CH3COOH(aq) + NaOH(aq) H2O(l) + NaCH3COO(aq)

Assume you titrated a sample of vinegar using 0.145 M of sodium hydroxide. The results of this titration are shown in the following table.

Use the data in the above table to determine the vinegar's acetic acid concentration in moles per liter.

(b)

Calculate the percent acetic acid in the titrated vinegar. Note that 1% = (1 g acetic acid/100 mL vinegar) × 100%.

%

Table 2: Titration Data for Vinegar Volume of Vinegar Titrated (mL) 5.00 Initial Volume of NaOH (mL) 0.10 Final Volume of NaOH (mL) 29.05

Explanation / Answer

mol of NaOH = MV

Vbase = (29.05-0.10) = 28.95 mL = 28.95*10^-3

mol of base = MV = 0.145 * 28.95*10^-3 = 0.004197 mol of base

ratio is 1:1

mol of acid = mol of base = 0.004197

mol of acid = 0.004197

[Acid] = mol of aicd / Vacid = (0.004197) / (5*10^-3) = 0.8394 M of acetic acid

b)

% mass of acid = mass of acid / mass of solution * 100%

mass of acid = mol*MW = (0.8394*60) = 50.364 g of acetic acid

mass of solution = 1 Liter = 1000 mL = 1000 g

% mass = 50.364 / 1000*100 = 5.0364 % by mass

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