Problem: Calculate the [H3O+] of the following polyprotic acid solution: 0.135M H2CO3.Calculate the pH of this solution.

FREE Expert Solution

We’re being asked to calculate the [H3O+] and the pH of a 0.135 M H2CO3. Carbonic acid (H2CO3) is a diprotic acid, it can donate two protons (H+and it will have two equilibrium reactions

To calculate for pH, we use the following equation:

pH=-log [H+]


(Ka values can be found in books or online):

Ka1 = 4.3x10-7

1st equilibrium reaction:                H2CO3(aq) + H2O(l) → HCO3­-(aq)H3O+(aq

Ka2 = 5.6x10-11

2nd equilibrium reaction:               HCO3-(aq) + H2O(l) → CO32­-(aq)H3O+(aq)

H3O+(aq) is also produced from the 2nd equilibrium reaction

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Problem Details

Calculate the [H3O+] of the following polyprotic acid solution: 0.135M H2CO3.

Calculate the pH of this solution.

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Diprotic Acid concept. You can view video lessons to learn Diprotic Acid. Or if you need more Diprotic Acid practice, you can also practice Diprotic Acid practice problems.