Answer: The chemical reaction is given below.
Step-by-step explanation:
Double displacement reactions are defined as the reactions in which exchange of ions takes place. The general equation for this reaction follows:

The chemical equation for the reaction of phosphoric acid and potassium hydroxide follows:

By stoichiometry of the reaction:
1 mole of phosphoric acid reacts with 3 moles of potassium hydroxide to produce 1 mole of potassium phosphate and 3 moles of water.
This is also known as neutralization reaction.