Question

1. How would you prepare a liter of "carbonate buffer" at a pH of 10.07? You are provided with carbonic acid (H₂CO₃), sodium hydrogen carbonate (NaHCO₃), and sodium carbonate (Na₂CO₃).

Please give an explanation.

2. Provide the mole ratio to support your answer. (Give your answer in the form base : acid.)

Answer 1

ph = 10.07

This is a buffer so:

pH = pKa2 + log(A-2/HA-)

Ka2 = 4.7 × 10⁻¹¹

pKa = -log(Ka2) =-log(4.7 × 10⁻¹¹⁾= 10.33

substitute

pH = pKa2 + log(A-2/HA-) = 10.33 +  log(A-2/HA-) = 10.07

Solve for ratio

log(A-2/HA-) = 10.07-10.33 = -0.26

CO3-2 / HCO3 -=0.5495

CO3-2 = 0.5495*HCO3

If you need V = 1L then

[Na2CO3] = 1M

[NaHCO3] = 0.5495 M

2)

mole ratio

bse: acid must be... 1 : 0.5495