Question

10 pts

Question 2. Suppose 5*10-4 M chloroacetic acid

(a) What are the sources of proton? Which proton source can be ignored and why?
(b) What is the pH of the solution?
(c) Show and confirm any assumptions made in calculation of pH.
(d) What is analytical concentration of chloroacetic acid?

Answer 1

Thus, ak( 5x10 4 20) stucture of chloroacetic acid is, aion + avholde 0-H The proton so this is the undicated as 'H'a here, is the only replaceable proton of chloroactic acid (pka = 2:87). only proton source from alloroacetic acid. b) chloroacetic acid being a weak acid, a part of it dissociates in aqueous solution to give UCH₂COOH UCH₂ coo- + Ht .. The arid dissociation constant ka = [UCH,600] [H] [uch,6004] Now, at equilibrium net was consider that xM dctcook undergoes dissociation. Therefore, [uch,600] [**] = =xM at equilibrium and [cach,000H] = (5x10" - x)m at equilibrium x.x ka - x (5x1024 As, UCH₂COOH is a weak acid, we can consider that very small amount of ut undergoes dissociation a . :. Ka x² 5x10 4 ka of chloroacetic acid = 13x10 3 04, X = 6.5X107 O, K2 PHs - log [mt] [H] 16.5x107 dogſ (6.5x107) = 3.09

c) uts al CH₂COOH is a weak acid, it has a low propensity to dissociate. Hence, while calculating ut it is assumed that very little quantity of the chloroacetic acid undergoes dissociation" sherefore, for Ka cabulation at equilibrium we consider [uch,cooH] at equilibrium to be effectively equal to [uch, cook] present initially moles of d) Analytical concentration is the total number of a solute present in le e of of a a solution. Iture fore, here the analytical concentration of UCH₂COOH in the initial concentration ан, that is 5 x 10-4 cooH of M.