Calculate the pH of a solution that is 0.295 mol L^-1 in sodium formate (HCOONa)and 0.205 mol L^-1 in formic acid (HCOOH). The K_a of formic acid is 1.77 × 10^-4. A)3.910 B)3.587 C)13.84 D)10.10 E)4.963

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The correct answer is A because the pH of the solution 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 formic acid is 1.77 × 10-4, the concentration of the conjugate base (sodium formate) is 0.295 mol L-1, and the concentration of the acid (formic acid) is 0.205 mol L-1. Plugging these values into the equation, we get: pH = 1.77 × 10-4 + log(0.295/0.205) = 3.910.

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