A research laboratory needs 500.0 mL of a buffer solution with pH 8.20 and an overall…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A research laboratory needs 500.0 mL of a buffer solution with pH 8.20 and an overall formal concentration of 0.100 M based on the base Tris [(HOCH2)3CNH2] and its conjugate acid. The pKa of the conjugate acid is 8.06 at 25 °C. Only solid Tris base (formula mass 121.14 g·mol⁻¹) and 1.00 M hydrochloric acid solution (density 1.02 g·mL⁻¹) are available.
(1) Determine the numerical ratio [Tris]/[TrisH+] required for the buffer to have the target pH.
(2) Calculate the moles of Tris base and TrisH⁺ that must be present in 500.0 mL of the 0.100 M buffer.
(3) Determine the mass of solid Tris base that must be weighed out.
(4) Calculate the volume of 1.00 M HCl that must be added to protonate the required fraction of Tris base.
(5) If a 6.00 M HCl solution were used instead of the 1.00 M solution, state how the volume of acid required would change and discuss one practical advantage and one potential hazard associated with using the more concentrated acid.