Question

HC,H3O2(aq) + H20() 근 H,O+(aq) + C2H30,-(aq) hedissaciation of ethanoic acid, HC,H,0,(aq), is represented above. A student is given the task of determining the value of K, for HC H,O(aa) using two different experimental procedures (a) The student is first asked to prepare 100.0 ml of 0.115 M HC,H,0 (aq) using a 2.000 M standard solution (1) Calculate the volume, in mL, ot 2.000 M HC HO aq) the student needs to prepare I 0.115 M HC H,O (ag) (i) Describe the procedure the student should use to prepare 100.0 mL of 0.115 M HC,H,O,(a) using appropriate equipment selected from the list below. Assume that the student uses appropriate safety equipment 100 mL beaker 100 mL. graduated cylinder · 100 mL volumetric flask .Eye dropper 500 mL wash bottle filled with distilled water 2.000 M HC2H,O(aą) in a 50 mL buret (b) Using a pH probe, the student determines that the pH of 0.115 M HC,H,O,(aą) is 2.92. 6) Using the pH value, calculate the value of K, for HC,H,O,(ag) (i) Calculate the percent dissociation of ethanoic acid in 0.115 M HC,H,O,(a) In a separate experimental procedure, the student titrates 10.0 mL of the 2.000 M HC,H,0,(aą) with an NaOHaą) solution of unknown concentration. The student monitors the pH during the titration. The following titration curve was created using the experimental data presented in the table.

Answer 1

(i) suppose v ml of 2(m) ethanoic acid is needed to prepare 100 m l 0.115(m) ethanoic A so, 2 times vb = 100 times 0.115 or v = 100 times 0.115/2 = 5.75 mol (ii) Take 5.75 m l ethanoic A from bucket into a 100 m l volumetric Hark and make up the volume up to mark by using water from wash bottle to prepare 100 ml 0.115(m) ethanoic A solution b) for a weakly dissociating acid P^H = 1/2 p^ma - 1/2 log e 2.92 = 1/2 p^k a - 1/2 log 0.115 p^ka = 8.78 or k a = 10^-6.78 = 1.66 times 10^7 we also known that degree of dissociation = alpha = squareroot k a/c = 0.0012 or 0.12 percent