Question

2. A soft drink has a pH around 2.7 due partially to its high H2CO3
content.
a. If all the acidity in the beverage was generated by bubbling it with pressurized CO2(g), what
PCO2
would have been required in the bubbles?
b. What would the pH of the solution be if it was in equilibrium with a PCO2 of 4 atm?
c. The pH of the solution is actually kept low by a combination of dissolved CO2 plus
phosphoric acid. Assuming PCO2 is 4 atm in the bottle, what concentration of H3PO4 must be
added to solution to reach pH 2.7?

Answer 1

Answer:

Ka=[H3O+]×[HCO−3][H2CO3]

4.3×10−7=[H3O+]×[HCO−3]5.0×10−2.

Ka=[H3O+]×[CO2−3][HCO−3]

4.8×10−11=[H3O+]×[CO2−3][1.47×10−4]