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Another way to express acid strength is by using pK Learning Goal: To understand

ID: 552279 • Letter: A

Question

Another way to express acid strength is by using pK Learning Goal: To understand the relation between the strength of an acid o Another way to express base strength is by using pKi a base and its pK, and pkb values The degree to which a weak acid dissociates in solution is oven by its acid-ionization consfant, K For the geneic Part A A new potential heart medicine, code-named X-281, is being tested by a pll, you are told that X-281 i company is interested in the drug's K, value because only the dissociated form of the chemical is active in preventing HA(aq) = A"(aq) + H, (m) pharmaceutical company, Pharma-pil As a research techrician at Pharma nd the acid-ionication constant is given by s a mongprotic weak acid, but because of security concems, the actual chemsic all formula must remain top secret. The To fnd the pk, of X-281, you prepare a 0 083 Mtest solution of X-281 at 25 of X-2817 cholesterol buildup in artenes C The ph of the solution is determined to be 2 40. What is the pK mlaty, the degree to which a weak base reacts with H20 solution is given by its base-ionization constant, K e generic weak base, B Express your answer numerically Hints Fo B(an) + H2O()-BEI. (aq) + OH (aq) d the base-ionization constant is given by Subenit My Answers Give Up Part B

Explanation / Answer

Ka = [A-][H+]/[HA]

here [H+] = [A-]

Ka = [H+]^2/[HA]

logKa = log[H+]^2 - log[HA]

-logKa = -2log[H+] + log[HA]

pKa = 2pH + log[HA]

pH = 1/2(pKa - log[HA])

2.4 = 1/2(pKa - log(0.083))

pKa = 3.719