CHE 168Spring18MCGREGOR Activities and Due Dates Topic 5 Syn

-CHE 168-Spring18-MCGREGOR >Activities and Due Dates Topic 5 Synthesis 2018 11:55 PM 0/10 2/25/2018 12:48 AM 3 of 6 Incorrect apling Learning Complete the Ki2 expression for HCOs in an aqueous solution. Ka2 = 4.69 × 10-1 =

Solution

First deprotonation reaction will be:

H₂CO₃ (aq) + H₂O (l) ----> HCO₃^- (aq)+ H₃O⁺(aq)

Ka₁ = [HCO₃^-] [H₃O⁺] / [H₂CO₃]

Second deprotonation reaction will be:

HCO₃^- (aq)+ H₂O(l) ----> CO₃^2-(aq) + H₃O⁺(aq)

Now, Ka₂ = [CO₃^2-] [H₃O⁺] / [HCO₃^- ]

Thus, Ka₂ = 4.69 x 10^-11 =  [CO₃^2-] [H₃O⁺] / [HCO₃^- ]

*[H₃O⁺] can also be written as [H⁺].