What is the pH of a 0.42 M solution of sodium propionate,NaC₃H₅O₂,at 25°C? (propionic acid,HC₃H₅O₂,is monoprotic and has a K_a = 1.3 × 10^-5 at 25°C..K_w = 1.01 × 10^-14 ) A) 6.06 B) 4.75 C) 11.10 D) 7.94 E) 9.25

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Sodium propionate is the salt of a weak acid (propionic acid) and a strong base (NaOH). When it dissolves in water, it produces propionate ions, which react with water to form propionic acid and hydroxide ions, making the solution basic. The pH can be calculated using the formula for the base ionization constant (Kb) of the propionate ion, derived from Kw and Ka of propionic acid. Kb = Kw / Ka = (1.01 × 10^-14) / (1.3 × 10^-5) = 7.77 × 10^-10. Using the formula for Kb and the concentration of propionate ions, we can find pOH and then pH = 14 - pOH. The calculation yields a pH greater than 7, indicating a basic solution. Among the options, 9.25 is the only one that fits this description.

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