The composition diagram, or alpha plot, for the important acid–base system of carbonic acid, H₂CO₃, is illustrated. (See Study Question 117 for more information on such diagrams.)    

(a) Explain why the fraction of bicarbonate ion, HCO₃⁻, rises and then falls as the pH increases.
(b) What is the composition of the solution when the pH is 6.0? When the pH is 10.0?
(c) If you wanted to buffer a solution at a pH of 11.0, what should be the ratio of HCO₃⁻ to CO₃²⁻?

Data given in Question 117

Transcribed Image Text:

Alpha 1.00 0.80 0.60 Fraction of H₂CO3 0.40 0.20 0.00 3 Fraction of HCO3 5 7 9 PH Fraction of Co-²- 2- 11 13 15