Vinegar

Determination of the Ka of a Weak Acid Introduction: Acids and radicals ar oft described as being weak or salubrious. While this classification seems somewhat arbitrary, other to a greater extent quantifiable descriptors exist. For bitings, Ka nurses are commonly single-valued functiond. The ionization of an acid puke be shown by the following equation: HA(aq)(H+(aq)+A-(aq)(Eq. 1) Since an chemic equilibrium exists, an equilibrium constant, Ka, can be written: Ka=[H+] [A-](Eq. 2) [HA] The Ka value is an character of acid strength. The larger the value of the Ka, the stronger the acid. This value is mark of the acid and can be used to help come in an chartless acid. A similar system exists for sales booths (Kb). Two methods whitethorn be used to govern the Ka value. Both methods require the use of a pH meter. In the first method, a audition of acid is titrated with base. The pH values are plotted vs. the slew of base added. The equivalence draw is determined from the graph. Next, the garishness of base central to the equivalence point is found, and the pH at this volume is noted. The [H+] identical to this pH is equal to the Ka for the acid. At a point midway to the equivalence point, [H+] = [HA] = [A-] for a monoprotic acid. Canceling out [A-] and [HA] in comparison 2 gives Ka = [H+]. The second method for determining Ka values involves a one-half volume method. A solution of the acid is active and divide in half as accurately as possible. unrivaled portion is titrated to its endpoint with phenolphthalein. The both portions are accordingly recombined, and the pH of the resulting solution is measured. Since half of the acid has been titrated, [H+] = [HA] = [A-]. Again, if [A-] and [HA] are canceled in Equation 2, Ka = [H+]. The pH value of the combined solutions can be born-again to [H+] to give a Ka value. Purpose: The purpose of this investigate is to determin e the Ka value for a weak acid by two method! s: potentiometric titration and half volume...If you want to get a bountiful essay, order it on our website: BestEssayCheap.com

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