Calculate the pH of a buffer that is 0.145 M HC₂H₃O₂ and 0.202 M KC₂H₃O₂.The K_a for HC₂H₃O₂ is 1.8 × 10^-5. A) 4.89 B) 9.01 C) 4.74 D) 5.05 E) 4.60

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The correct answer is A because the pH of a buffer can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid. In this case, the pKa of HC2H3O2 is 1.8 × 10-5, [A-] is 0.202 M, and [HA] is 0.145 M. Plugging these values into the equation, we get: pH = 1.8 × 10-5 + log(0.202/0.145) = 4.89.

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