Ph Buffers And Determination Of PKA For A Weak Acid

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Practical 3 – pH, Buffers and Determination of pKA for a Weak Acid. Introduction This experiment was designed to test the pH changes of a weak acid, acetic acid, when it is titrated with a strong base, NaOH. We conducted this experiment so that we could obtain a pH titration curve and from this, we can correlate and signify the relationships between pH, pKA, and the ratios between the acetic acid and NaOH. This practical was key to developing our understanding of buffers and how they accept and donate protons, how this inhibits pH changes, and how this mechanism can be used for in vitro laboratory experiments. Acetic acid, CH3COOH, is described as a ‘weak’ acid as when it dissociates in water, only a very small proportion, one proton, is transferred to a water molecule. (Experimental Biology Lab Manual 2017) This experiment would also allow us to determine the pKA, the measurement of an acid’s ability to give up its protons to water. The addition of NaOH to acetic acid, results in more of the acetic acid to be dissociated into CH3COO- and H+ ions. These protons then can react with the OH- ions to form water. This reaction is in equilibrium and is fairly rapid. The Henderson-Hasselbach equation can be used to determine the pH: A- = the molar concentration of the conjugate base HA = the molar concentration of the conjugate acid (Experimental Biology Lab Manual 2017) During this experiment, it was vital that we performed accurate pipetting to result in the most reliable
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