Titration of Acetic Acid in Vinegar A. Overview of Concepts Recall the definitions of Acids and Bases Acids in aqueous s

[answerhappygod]

Titration Of Acetic Acid In Vinegar A Overview Of Concepts Recall The Definitions Of Acids And Bases Acids In Aqueous S 1 (176.95 KiB) Viewed 26 times

Titration Of Acetic Acid In Vinegar A Overview Of Concepts Recall The Definitions Of Acids And Bases Acids In Aqueous S 2 (179.69 KiB) Viewed 26 times

Titration of Acetic Acid in Vinegar A. Overview of Concepts Recall the definitions of Acids and Bases Acids in aqueous solution dissociate (ionize) to generate protons, H+ (aq) and anions, A- (aq). Acids are able to donate that H+ to another compound. HA (aq) → H+ (aq) + A- (aq) Bases in aqueous solution dissociate (ionize) to generate cations, M+ (aq) and OH- (aq). Bases are able to accept H+ from another compound. MOH (aq) → M+ (aq) + OH- (aq) When an acid and base are mixed together, the H+ and OH - react in a double replacement reaction to form water. This reaction is known as neutralization. Equation: Full Ionic Equation: Net Ionic Equation: Note that in the equation, the number of H+ and the number of OH- react 1:1. So, in order the have a complete neutralization of an acid or a base, there must be equal number of moles of H+ and OH-. HA (aq) + MOH (aq) → H₂O (1) + MA (aq or s) H+ (aq) + A- (aq) + M+ (aq) + OH- (aq) → H₂O (1) + A- (aq) + M+ (aq) H+ (aq) + OH- (aq) → H₂O (1) The procedure in which one measures the amount of one reactant required to react completely with a second reactant is known as titration. A convenient way of measuring the amount of acid in a sample involves titrating the acid solution with a solution of base in which the concentration is known (a standardized base). B. Practical Application: Titrating Acetic Acid in Vinegar. In this exercise, you will determine the concentration of acetic acid in a sample of vinegar by titration, in other words, you will be measuring the exact amount of NaOH needed to react with (or neutralize) the acetic acid. Equations describing the reaction between acetic acid and sodium hydroxide are shown: Equation: Full Ionic Equation: Net Ionic Equation: 1. Procedure HC₂H3O2 (aq) + NaOH (aq) → H₂O (1) + NaC₂H3O2 (aq) H+ (aq) +C₂H3O2 (aq) + Na+ (aq) + OH- (aq) → H₂O (1) + C2H3O2 (aq) + Na+ (aq) H+ (aq) + OH- (aq) → H₂O (1)
a) Setting up for titration: Transfer exactly 5.00 mL of vinegar to a 250 mL Erlenmeyer flask as well as about 25 mL of deionized water. To this mixture add 2-3 drops of phenolphthalein indicator solution. . . Obtain a 50.00 mL buret and first rinse it with two small (about 5 mL) portions of the standardized NaOH. Then using a funnel, add NaOH to the buret to a volume of about 35 mL. Pay close attention to how the buret is marked; the 50.00 mL mark is near the bottom of the buret shaft while the 0.00 mL mark is near the top. Now, dislodge any bubbles that may be trapped by opening the stopcock and allowing a few mL of NaOH to flow out of the buret while lightly tapping near the buret tip. Fill the buret with the standardized NaOH solution so that the meniscus is at the 0.00 mL mark near the top of the buret. Place the buret in a buret clamp, and place the flask with the vinegar solution directly under the tip of the buret. In order to best monitor changes in color of the indicator solution, it is a good idea to place the Ehrlenmeyer flask on top of a white surface. b) The titration procedure: Begin adding the NaOH solution from the buret into the vinegar solution in ~ 0.5-1 mL increments, making sure to mix the contents of the flask by swirling for several seconds after each addition. Continue adding NaOH and subsequently swirling. Expect to see the pink color of the indicator appear at the point where the NaOH makes contact with the flask solution, and then clear with swirling. When the pink color of the indicator becomes more persistent, and slower to disappear, decrease the volume of NaOH additions to one drop at a time. When one drop generates a faint, but permanent pink color throughout the solution, the titration is complete. Make sure to record the total volume of NaOH used to reach the end point of the titration. c) Calculating the % Acetic Acid in Vinegar
Chemistry 19 - Santa Monica College Concentration of NaOH: Initial NaOH level in buret Final NaOH level in buret at titration endpoint Net Volume of NaOH added for titration endpoint (Final - Initial) Moles of NaOH for titration endpoint (Molarity x Volume) Moles of HC₂H302 reacted at titration endpoint (= moles NaOH) Mass of HC2H302 reacted at titration endpoint (moles x molar mass) % (m/v) HC₂H30₂ in vinegar (grams in 5.00 mL X 100) Report the Average % (m/v) of acetic acid in vinegar: Trial 1 0 mL 26.50 mL NaOH (aq) + HC2H302 (aq) -> H2O (1) + NaC2H3O2 (aq) The concentration of the NaOH used was 0.1117 M Trial 2 26.50 mL 48.45 mL