Soper-548d0ab44b774Lab 20-2 - Lab 20 pH Titration Phosphoric Acid in Cola Drinks Madison Bunker Alec Hendrix I did not copy this work from any other

# Soper-548d0ab44b774Lab 20-2 - Lab 20 pH Titration...

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Lab 20: pH Titration: Phosphoric Acid in Cola Drinks Madison Bunker Alec Hendrix September 29, 2014 I did not copy this work from any other students; current students or old lab reports. Data and Results A. Data Tables and Plots a. Table 1. Standardization of NaOH b. Table 2. Initial Parameters of Titration c. Table 3. Data for Titration of Cola d. Plot 1. Titration Curve with Approximate First Derivative 0 2 4 6 8 10 12 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 pH ΔpH/ΔV Volume of Titrant pH First Derivative of the Titration Curve Equivalence point Equivalence point Halfway Point Halfway Point e. Table 4. Determination of K a Values B. Sample Calculations a. Standardized molarity of NaOH solution Trial 1: .066 gKHP 204.2 g / mol = 3.232 10 4 mol .03280 L = .00985 M b. Initial concentration of phosphoric acid in cola sample First equivalence point occurs after 6.41 mL of NaOH is added, so [ H 3 PO 4 ] = mol NaOH at equivalence point initial volume = .01 M .00641 L .02 L = .003205 M c. K a1 calculated non-graphically, from initial pH and [H 3 PO 4 ] [H 3 PO 4 ]=.003205M [H 3 O + ]=10^-2.42=.003802 *error must have occurred either when measuring the initial pH or when calculating the first equivalence point because the [H 3 O + ] could not be greater than the initial [H 3 PO 4 ]. + ¿ H 3 O ¿ ¿ ¿ H 2 PO 4 ¿ ¿ ¿ K a = ¿ Note: This is clearly a wrong answer because K a cannot be negative, but for the sake of demonstrating how to calculate the K a1 non-graphically the methodology is correct.  #### You've reached the end of your free preview.

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• Fall '12
• SOPER
• pH, Equivalence point, Sodium hydroxide, Cola Drinks
• • • 