Question

The diprotic acid h2co3 can produce two buffers depending on the ph of the solution. identify the conjugate acid/base pair from carbonic acid that would form the most basic buffer.

Answer 1

These are the choices for this question:
a) CO₃²⁻ and OH⁻
b) CO₃ and CO₃²⁻
c) H₂CO₃ and CO₂⁻³
d) H⁺ and H₂CO₃
e) H₂CO₃ and HCO₃⁻
This is the best answer for the choices given is e) but the HCO₃⁻ and CO₃²⁻ pair would be more basic than the carbonic / bicarbonate pair.

Answer 2

Considering the answers;
a) CO₃²⁻ and OH⁻
b) CO₃ and CO₃²⁻
c) H₂CO₃ and CO₂⁻³
d) H⁺ and H₂CO₃
e) H₂CO₃ and HCO₃⁻
The correct answer is e) H₂CO₃ and HCO₃⁻; however, the HCO₃⁻ and CO₃²⁻ pair would be more basic than the carbonic / bicarbonate pair. A buffer is a mixture of a conjugate acid-base pair that can resist changes in pH upon addition of an acid or a base. Carbonic acid is formed when carbon dioxide is dissolved in water; Bicarbonate buffer system consists of carbonic acid, a weak acid, and the bicarbonate anion, its conjugate base.