Chemistry Practice Problems Diprotic Acid Practice Problems Solution: Complete the Ka2 expression for H2CO3 in an aqueou...

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Solution: Complete the Ka2 expression for H2CO3 in an aqueous solution. Ka2 = 4.69 x 10-11

Problem

Complete the Ka2 expression for H2CO3 in an aqueous solution. Ka2 = 4.69 x 10-11

Solution

For this problem, we are asked for the Ka2 expression so we don't actually need to compute anything. We just have to set it up.

Know that H2CO3 (Carbonic acid) is a polyprotic acid which means we have more than 1 acidic hydrogen that can dissociate. In this specific acid, we have 2 acidic hydrogens. Shown below is the form of carbonic acid for every step that it losses each hydrogen. We also have the proper Ka's that we will use for each removal of hydrogen. Since we are asked for Ka2 we focus on the highlighted step and we start with the intermediate form in the center. 

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