# Experiment 17 PreLab (Snyder, Sarah R).docx - Buffer...

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Chapter 8 / Exercise 34
Intermediate Algebra: Connecting Concepts through Applications
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Buffer Solutions Experiment 17 Sarah Snyder Method 1: Determining the K a / pK a of Acetic Acid by pH Objective: The objective of this part of the experiment is to determine the K a and pK a by finding the concentration through titration, the pH a solution sing a pH meter and then use the formula for K a and converting it to pK a . Hypothesis: Buffer solutions resist drastic changes in pH when small amounts of either strong acids or strong bases are added. In this experiment we will make a buffer using a weak acid (acetic acid) and its conjugate base (acetate) from sodium acetate. When both the weak acid and its conjugate base are in solution, the weak acid (HA) is able to neutralize and any base that is added and the conjugate base (A - ) is able to neutralize any acid that is added as shown in the generic chemical equations: HA(aq) + OH - (aq) ↔ A - (aq) + H 2 O(l) for a weak acid neutralizing a base and A - (aq) + H 3 O + (aq) ↔ HA(aq) + H 2 O (l) for a conjugate base neutralizing an acid. The K a of a weak monoprotic acid is defined as + ¿ H 3 O ¿ ¿ ¿ A ¿ ¿ ¿ K a = ¿ and can be transformed into the Henderson-Hasselbalch equation, ¿ A ¿ ¿ ¿ pH = p K a + log ¿ . To experimentally determine K a and pK a of acetic acid, the concentration of the acid must be found first through the process of titration. Once the pK a value is determined, then you can predict the pH of the solution. The pK a value of acetic acid should be approximately 4.8. Variables: The independent variables are___________________________________. The dependent variable is ________________________________________. Experimental Procedure: Titration 1. Make 150mL of approximately 0.1M NaOH from 5.0M NaOH using a graduated cylinder to measure the 5.0M NaOH and a clean, dry and labeled 250mL Erlenmeyer
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Chapter 8 / Exercise 34
Intermediate Algebra: Connecting Concepts through Applications
Clark Expert Verified
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