Carbon dioxide dissolves in water to form carbonic acid, which is primarily dissolved CO2. Dissolved CO2 satisfies the equilibrium equation.

Question

The acid dissociation constants listed in most standard reference texts for carbonic acid actually apply to dissolved CO2. K=0.032 M/atm

For a CO2 partial pressure of 2.4×10-4 atm in the atmosphere, what is the pH of water in equilibrium with the atmosphere?

Answer 1

Since carbonic acid is primarily dissolved CO2, the concentration of H2CO3 can be taken as equal to that of dissolved CO2,
[H2CO3]=[CO2aq]
The equilibrium equation for the dissolution of gaseous CO2 can be used to calculate the [CO2(aq)] and, hence, the [H2CO3]. The [H2CO3] will then be used to calculate the pH. Dissolved CO2 satisfies the equilibrium equation
pH=5.609

Answer 2

can you show step by step how you got that pH?