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tem Problem 2 130 An aqueous solution containing 0.2M of sodium hydroxide is all

ID: 1036161 • Letter: T

Question

tem Problem 2 130 An aqueous solution containing 0.2M of sodium hydroxide is allowed to equilibrate with the atmosphere in an analytical laboratory where the temperature is kept at 25 C. The partial pressure of carbon dioxide in the atmosphere, Pco2, is101 atm, and the Henry's Law constant for carbon dioxide KH -10-15 mol.L/atm. Determine the pH and the total acid concentration, CTCOs, of the solution when equilibrium with the atmosphere is reached. How do you expect the concentration ??.??? to vary with jnitial concentration of NaOH in solution?

Explanation / Answer

Solution :-

[H2CO3] = Kh.PCO2

[H2CO3] = 9.99 X 10-6 mol.L

K1 =  [H+] [HCO3-] / [H2CO3]

K1.[H2CO3] = [H+]2

[H+]2 = 5.01 X 10-12

[H+] = 2.237 X 10-6 and [HCO3-] = 2.237 X 10-6

pH = 5.65

K2 = [CO32-] [H+] / [HCO3-]

[CO32-] = 4.69 X 10-11

Total acid concentration = [CO32-] + [HCO3-] +  [H2CO3]

Total acid concentration = 1.223 X 10-5