Geothermal resource development

For exercise 1c.

When the water is in contact with calcite, we need to consider the reaction:

CaCO₃ + H⁺ ⇌ Ca²⁺ + HCO₃⁻

At equilibrium, the concentration of dissolved [CO_2(aq)] in water is related to the bicarbonate concentration and pH:

HCO₃⁻ + H⁺ ⇌ H₂O + CO_2(aq)

The equilibrium constant for the dissolution of CO_2(aq) in water is:

K CO_2(aq)  = [CO_2(aq)]/([H⁺][HCO₃⁻]) = 4.45 x 10^-7 mol/L  at 25°C 

As the reaction is reversible, it can be read from left to right or vice-versa:

H₂O + CO_2(aq) ⇌ HCO₃⁻ + H⁺  

K CO_2(aq)  = ([H⁺][HCO₃⁻])/[CO_2(aq)] = 1/4.45 x 10^-7 mol/L  at 25°C 

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As a reminder, exercises are due October 16th, at the end of the class.