So, first we must write the odor ionization reaction for water. So two moles of water react to produce 1 mol of conjugate acid and 1 mol of conjugate base. Now, let's write the equilibrium constants equation or expression for our odorionization reaction. So, Kw is equal to concentration of hydronium times the concentration of hydroxide. So we know our Kw. That's a constant at a 25 degree Celsius, it's ten to negative 14.