(c) A student was asked to determine the thermodynamic properties, 4Hº, and Asº for the dissociation of a weak acid by m

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C A Student Was Asked To Determine The Thermodynamic Properties 4ho And Aso For The Dissociation Of A Weak Acid By M 1 (161.5 KiB) Viewed 71 times

(c) A student was asked to determine the thermodynamic properties, 4Hº, and Asº for the dissociation of a weak acid by measuring the acid dissociation constant (Ka) at different temperatures. The student was provided a sample of acetic acid and the measured data are listed in Table 2. The student was also reminded that the acid dissociation constant (Ka) is given by: ArGº = –RTInka (2.5) and Gibbs Free energy is defined by: 4,6° = Ayhº – tasº (2.6) == (i) Starting from equations (2.5) and (2.6), Derive the van't Hoff equation: АН” AS InK = - + RT (2.7) R [2 marks] (ii) Use the van't Hoff equation to determine the ArG°, ,Hº, and Asº for acetic acid. [8 marks] Table 2 Acid dissociation constant (Ka) determined for acetic acid as a function of temperature. T (°C) Kax 105 0 1.657 5 1.700 10 1.729 15 1.745 20 1.753