Polyprotic buffers (17 pts) Ascorbic acid (H&COs] Vitamin C) is a diprotic acid. HO OH H pka - 4.25 HO H pKa - 11.79 H HO CH,OH HO CH,OH HO CHO A) What is the pH of a 0.05 M solution of disodium ascorbate (NazHeCEO6) (answer questions 1-3 below)? 1) What value, which describes the relevant equilibrium but is not explicitly given above, do you need to calculate before you can solve this problem in the usual way? (2) 2) What is the value of this? (Show work) (2) 3) What is the pH of the solution? (Show work) (4) B) Ascorbic acid is sensitive to oxidation in its fully deprotonated form, so usually Vitamin C is given as monosodium ascorbate (NaHC606). 1) Regarding polyprotic buffers, what "class" or type of buffer salt is NaHC606? (1) 2) What is the pH of 0.1 M NaHC606? (4) C) How many equivalents of 0.1 M NaOH are needed to titrate a 0.05 M ascorbic acid (HBC606) solution to pH 7.4? (Read the question carefully! Beware of irrelevant information) (4)

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