The variation of the ionic product of water () with temperature is sometimes plotted visually as ver — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

The relationship follows the van 't Hoff equation: $\log K_w = -\frac{\Delta H^\circ}{2.303RT} + C$. Because the auto-ionization of water is an endothermic process, $\Delta H^\circ$ is positive. Therefore, the term $-\frac{\Delta H^\circ}{2.303R}$ is a negative constant. A plot of $\log K_w$ (y-axis) versus $1/T$ (x-axis) visually yields a perfectly straight line with a strictly negative slope. The visual slope directly equals $-\frac{\Delta H^\circ}{2.303R}$.