pH of water is 7.0 at 25°C. If water is heated to 70°C, the — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

The autoionization of water ($\text{H}_2\text{O} \rightleftharpoons \text{H}^+ + \text{OH}^-$) is an endothermic process. Heating water shifts the equilibrium to the right, increasing both $[\text{H}^+]$ and $[\text{OH}^-]$ equally. Because $[\text{H}^+]$ increases, the pH decreases (since $\text{pH} = -\log[\text{H}^+]$). However, since $[\text{H}^+]$ still perfectly equals $[\text{OH}^-]$, the water remains chemically neutral.