When carbon dioxide dissolves in water, it undergoes a

Chapter 18, Problem 97P

(choose chapter or problem)

When carbon dioxide dissolves in water, it undergoes a multistep equilibrium process, with \(K_{\text {overal }} 4.5 \times 10^{-7}\), which is simplified to the following:

                \(\begin{array}{l} \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{H}_{2} \mathrm{CO}_{3}(a q) \\ \mathrm{H}_{2} \mathrm{CO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons \mathrm{HCO}_{3}^{-}(a q)+\mathrm{H}_{3} \mathrm{O}^{+}(a q) \end{array} \)

(a) Classify each step as a Lewis or a Brønsted-Lowry reaction.

(b) What is the pH of nonpolluted rainwater in equilibrium with clean air ( \(\mathrm{P}_{\mathrm{CO} 2}\) in clean air \(3.2 \times 10^{-4} \mathrm{~atm}\); Henry’s law constant for \(\mathrm{CO}_{2}\) at \(25^{\circ} \mathrm{C}\) is 0.033 mol/Latm)?

(c) What is \(\left[\mathrm{CO}_{3}{ }^{2-}\right]\) in rainwater (\(\mathrm{K}_{\mathrm{a}} \text { of } \mathrm{HCO}_{3}{ }^{-}=4.7 \times 10^{-11}\))?

(d) If the partial pressure of \(\mathrm{CO}_{2}\) in clean air doubles in the next few decades, what will the pH of rainwater become?

Equation Transcription:

Koverall  4.5x10-7

PCO2 

3.2x10-4 atm

CO2

25°C

\(0.033 \mathrm{~mol} / \mathrm{L} \cdot \mathrm{atm}\)

[CO32 ⎺ ]

Ka of HCO3⎺  = 4.7x10-11

CO2

Text Transcription:

K_overall  4.5x10^-7

 

CO_2(g) + H_2O(l)  ⇌  H_2CO_3(aq)

 

 H_2CO_3(aq) + H_2O(l)  ⇌ HCO_3⎺ (aq) +H_3O + (aq)

 

P_CO2

3.2x10^-4 atm

 

CO_2

 

25°C

 

0.033 mol/L times atm

 

[CO_3^2 ⎺ ]

 

K_a of HCO_3⎺  = 4.7x10^-11

 

CO_2