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All odd slides - What is pH pH is defined as the negative...

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pH is defined as the negative logarithm of the hydrogen ion concentration pH = -log [H ] low pH values represent the highest [H + ] Henderson-Hasselbalch equation: the relationship between pH and the ratio of acid and conjugated base concentration . pH = Pk + log [A - ]/[HA] (conjugate base/conjugate acid) What is pH?
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To titrate several different samples and analyze titration behavior. To realize the importance of pH and Buffer - Henderson-Hasselbalch equation - The importance of pH - The importance of buffer To learn how to use a pH meter (optional). Titration Analysis
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The Importance of pH in Biological Systems Biological reactions depend on strict regulation of hydrogen ion [H + ] concentration. Change in pH affect [H + ] concentration: a) affect rates of enzymatic reactions b) denature proteins – complete loss of activity
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The Importance of Buffer in Biological Systems Buffer Solution: 1) Weak conjugated acid-base solution containing both [A - ] and [HA]. Has ability to resist changes in pH when modest amount of acid or base are added. when a strong acid is added, the H + ions will be consumed by the conjugate base in the buffer, thereby removing most of the added H + from the solution: H + + A - HA When a strong base is added, the OH - ions will be neutralized by the acid in the buffer: OH - + HA A - + H 2 O 2) Effective range: 1 pH unit above and below its pKa. 3) Buffering capacity is determined by the concentration of buffer and its pKa.
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Fruit juices are natural buffers. The tartness of pure fruit juices is largely due to a group of organic acids: 4 6 5 The fruit juice industry in the US alone is worth over $12 billion per year
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4 samples: distilled water , 0.05 M acetic acid , apple juice , cranberry juice. First, acidify each sample with 1.0 M HCl (drop by drop) until pH is ~1.8 Titrate acidified solution with 2ml aliquots of NaOH, mix and measure pH. Repeat until pH is >11. Record all values in Table 1. Rinse pH meter w/ DI water after every sample. Magnetic Stirrer Procedure How to use a pH meter?
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4 samples (50 ml each) distilled water, 0.05 M acetic acid, apple juice, cranberry juice acidify each sample with 1.0 M HCl (drop by drop) until pH is ~1.8 titrate with 2ml of NaOH, mix, measure and record repeat until pH is >11. Note: rinse pH meter w/ DI water after every sample waste disposal and clean-up Sample Procedure Outline
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Results and Analysis 1. Complete data table 1. 2. Make titration plot. 3. Answer question 2. Post-lab write-up: Observation & Results (3 pts) - Observation / Deviation: 1 pt - Table 1: 2 pts Analysis & Conclusion (6 pts) - Question 1 (plot): 3 pts - Question 2: 2 pts - Conclusion (explanation): 1 pt 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 2 4 6 8 10 12 14 16 18 ml of NaOH added pH H2O CH3COOH Apple Cranberry
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Clean-up and Waste Disposal Clean-up: - Rinse and blot dry pH meter. Recap the pH meter. - Used Glass Pipets: openings point down in the pipet jar.
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