Mixing nitric acid (HNO3) and potassium hydroxide (KOH) results in the formation of potassium nitrate (KNO3) and water (H2O). The reaction between these two substances can be represented as:

HNO3 + KOH → KNO3 + H2O

Potassium nitrate is a salt that is commonly used as a fertilizer, and it is also an ingredient in some explosives.