1 An enzymecatalyzed reaction was carried out in a 07 M carb

1. An enzyme-catalyzed reaction was carried out in a 0.7 M \"carbonate\" buffer, set at pH 7.7. As a result of the reaction, 0.02 M of OH was produced. pK, of \"carbonate/bicarbonate\" buffer is 6.3. a) Write the equilibrium conjugate-acid/conjugate-base reaction by which the b) Indicate the concentrations of bufering components (acidic and basic form of carbonate) o) What would be the final pH if no buffer were present? \"carbonate/bicarbonate\" buffer maintains a near constant plH at the end of the reaction.

Solution

a)

Equilibrium of carbonate/bicarbonate buffer

CO₃^2- + H₂O --> HCO₃^- + OH-

0.7 – x --> x + x

pH of buffer is given by:

pH = pKa + log([CO₃^2-] / [HCO₃^-])

b)

pH = pKa + log((0.7 – x) / (x))

7.7 = 6.3 + log((0.7 – x) / (x))

Solving we get, x = 0.027 M

[OH-] produced = 0.02 M

[CO₃^2-] = 0.7 – x + 0.02 M = 0.693 M

[HCO₃^-] = x – 0.02 M = 0.007 M

c)

[OH-] produced = 0.02 M

pOH = - log([OH-]) = 2

pH = 14 – pOH = 12