Carbonic acid, H2CO3, has two acidic hydrogens. A solution containing an unknown concentration of carbonic acid is titrated with potassium hydroxide. It requires 20.0 mL of 3.840 M KOH solution to titrate both acidic protons in 50.2 mL of the carbonic acid solution.
1. Write a balanced net ionic equation for the neutralization reaction. Include physical states.
2. Calculate the molarity of the carbonic acid solution.

1) Net ionic equation :

2) 0.765 M is  the molarity of the carbonic acid solution.

Explanation:

1) In aqueous carbonic acid , carbonate ions and hydrogen ion is present.:

..[1]

In aqueous potassium hydroxide , potassium ions and hydroxide ion is present.:

..[2]

In aqueous potassium carbonate , potassium ions and carbonate ion is present.:

..[3]

From one:[1] ,[2] and [3]:

Cancelling common ions on both sides to get net ionic equation :

2)

To calculate the concentration of acid, we use the equation given by neutralization reaction:

where,

are the n-factor, molarity and volume of acid which is

are the n-factor, molarity and volume of base which is KOH.

We are given:

Putting values in above equation, we get:

0.765 M is  the molarity of the carbonic acid solution.