A physiology experiment requires 100.0 mL of a buffer solution with pH 3.86 and an…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A physiology experiment requires 100.0 mL of a buffer solution with pH 3.86 and an overall formal concentration of 0.150 M, based on lactic acid (HC3H5O3, pKa = 3.86) and its sodium salt. The laboratory has 0.10 M lactic acid solution and anhydrous sodium lactate powder (molar mass 112.06 g·mol⁻¹).
(1) Part 1: Determine the ratio [HC3H5O3][C3H5O3−] necessary to achieve the target pH.
(2) Part 2: Calculate the moles of lactic acid and lactate ion required in 100.0 mL of the 0.150 M buffer.
(3) Part 3: Compute the volume of 0.10 M lactic acid solution that must be measured out.
(4) Part 4: Determine the mass of anhydrous sodium lactate that must be dissolved to provide the required amount of lactate ion.