WM Session 4:  Carbon Dioxide and Dissolved Carbonates

 

What is the pH of rain water?

 

CO2     Henry’s Law, C = kHP 

(kH = 3.4 x 10-2 for CO2 and the pressure of CO2 is 0.000350 atm)

 

 

                        CO2 (g) + H2O (l)  à  H2CO3 (aq)  à  H+ (aq) + HCO3- (aq)

 

 

SO2 and NO2:  Acid Rain:

 

 

 

 

 

Why do rocks dissolve?

 

            CO2 (g) + H2O (l)  + CaCO3 (s) à  Ca+2 (aq) +  2 HCO3- (aq)

 

            H2SO4 (aq) + CaCO3 (s) à  Ca+2 (aq) + SO4-2 (aq) + CO2 (g) + H2O (l)

 

 

 

 

 

 

What is the pH of some drinking water samples?

 

Source

[Ca+2], mM

[HCO3-], mM

pH

Grinnell

1.00

6.41

8.6

Des Moines

1.31

1.33

9.2

Chicago

1.35

2.30

8.2

Spring Water

0.29

0.60

7.4

 

 

            What is the reason for the pH of the drinking water samples? (natural or set)

 

 

 

 

 

 

 

 

What is alkalinity?  Which water sample has the highest alkalinity?

 

 

 

 

            How is alkalinity different than pH?

 

 

 

 

 

 

Why do virtually all fresh water samples contain bicarbonate as a principal species?

 

 

            How does bicarbonate concentration provide information on the geological source of the water?