Pure water dissociates according to the equation shown. H₂O(l) ⇌ H⁺(aq) + OH⁻(aq) The equilibrium constant for this reaction is known as Kʷ, the ionic product of water. Kʷ = [H⁺(aq)] [OH⁻(aq)] At 25°C, Kʷ has a value of 1.00 × 10⁻¹⁴ mol² dm⁻⁶. The pH of pure water at 25°C is 7.00. A student finds the pH of pure water at 35°C is 6.84. The student investigates how temperature affects the pH of pure water and determines a value for the enthalpy change for the dissociation of water, ΔH. The student records the pH of pure water at different temperatures. A line of best fit from the results of the student's investigation is shown in Fig. 2.1. [Figure 2.1]