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Lab 8 p H measurement and buffer preparation

Lab 8 p H measurement and buffer preparation. purpose. To learn how to prepare a buffer solution. 2) To learn how to measure pH of solution by different ways. Buffer: . Are Solutions which resist change in pH upon addition of small amounts of acid or alkali.

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Lab 8 p H measurement and buffer preparation

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  1. Lab 8pH measurement and buffer preparation

  2. purpose • To learn how to prepare a buffer solution. • 2) To learn how to measure pH of solution by different ways. Buffer: Are Solutions which resist change in pH upon addition of small amounts of acid or alkali

  3. Hydrogen-ion concentrations of aqueous solution are represented by pH. pH values range from 1-14

  4. Consists of :- • weak acidand its salt ( Acidic buffer ) • e.g CH3COOH / CH3COONa • b) weak base and its salt ( Basic buffer ) • e.g NH4OH / NH4Cl Henderson equation : for acidic buffer pH = pKa + log [salt] / [acid] The ratio of weak acid or base to its salt. Buffer Ratio

  5. Methods used for measurement of pH of solutions: pH meter pH paper Different colored papers each color indicates a unit pH value a sensitive electrode dipped into the solution

  6. You are supplied with 0.1 M Acetic acid and 0.1 M Sodium Acetate , Using Henderson equation , to prepare 20 ml buffer with different pH ( 3.7, 5, 5.7 ) ??? ( pKa of Acetic acid = 4.7 ) Henderson equation : for acidic buffer pH = pKa + log [salt] / [acid

  7. 10 ml CH3COONa 11 mL Buffer ??????? 20 mL Buffer As taken by Burette 1Ml CH3COOH 11 mL Buffer ??????? 20 mL Buffer 18.2 18.18 1.81 1.8

  8. Procedure: 1.Rinse a beaker with distilled water and then dry it. 2.Transfer ---ml of 0.1 M acetic acid and ---ml of 0.1 M sodium acetate into the beaker. 3.Measure pH of the buffer solution using: pH paper and comparing with standard colors corresponding to different pH values (approximate value). pH meter by immersing the electrode of pH meter into the buffer solution, wait for seconds till equilibrium and then read pH value

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