Question

Question:

The organic compound below is abbreviated Tris and is basic. The conjugate acid (TrisITT has a pKa of 8.10.

TrisH+ + H20 = Tris + H30 +

Tris is commonly used as a component in buffer solutions to study biochemical reactions.

a) A buffer solution is prepared by mixing 12.5 mL of 0.100 mol L- 1 HCl with 25.0 mL of0.100 mol L- 1 Tris. What is the pH of this buffer? Write all the equations used and explain your steps.

b) The buffer was used to study an enzyme-catalyzed reaction in which 0.00020 mol of H30+ was produced. What is the pH of the solution after the acid reacted with the buffer? Write all the equations used and explain your steps.

Answer 1

(a) pKa for conjugate acid = 8.10

volume of HCl = 12.5 mL, Molarity= 0.1M

volume of Tris = 25 mL, Molarity = 0.1 M

pH= pKa+ $\frac{log (Tris)}{HCl}$

$pH= 8.10 +\frac{log (0.1)}{0.1}= 8.10$

(b) mole of H₃O⁺ produced = 0.0002 mol

$pH= 8.10 +\frac{log (0.1)}{0.0002}= 7.90$