Answer to Question #89559 in General Chemistry for Lim Yoona

Question

A buffer solution is prepared by mixing 30.0 mL of 0.132 mol L-1 lactic acid (pKa = 3.86) and 70.0 mL of 0.243 mol L-1 sodium lactate. What is the pH of the buffer solution?

Answer 1

We will use this formula to count out the pH of the buffer solution.

pH = pK_a + lg(c(C₃H₅NaO₃) * V(C₃H₅NaO₃) / c(C₃H₆O₃) * V(C₃H₆O₃)) = 3.86 + lg(0.234 mol/L * 0.07 L / 0.123 mol/L * 0.03 L) = 3.86 + lg(0.01701/0.00396) = 3.86 + lg4.295 = 3.86 + 0.633 = 4.493.