How would I write a well-balanced chemical equation for a reaction between carbonic acid and potassium hydroxide?

When carbonic acid reacts with potassium hydroxide, we get potassium carbonate and water. This reaction can be written as:

`H_2CO_3 (aq) + KOH (aq) -> K_2CO_3 (aq) + H_2O (l)`

Here, carbonic acid is a weak acid and potassium hydroxide is a strong base. 

The above reaction is not balanced. A balanced equation has the same number of atoms of each element on both sides. Here, potassium, hydrogen, and oxygen are not balanced—you can count the number of atoms of each of these elements on both sides of the equation and verify.

The equation can be balanced and written as:

`H_2CO_3 (aq) + 2KOH (aq) -> K_2CO_3 (aq) + 2H_2O (l)`

Here we can see that 1 mole of carbonic acid reacts with 2 moles of potassium hydroxide and generates 1 mole of potassium carbonate and 2 moles of water.

Hope this helps.