Which of the following statements regarding the auto-ionization of water and its pH scale are correc — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

The auto-ionization reaction $H_2O \rightleftharpoons H^+ + OH^-$ is endothermic. Heating shifts the equilibrium forward, increasing $K_w$ and thus decreasing $pK_w$. A neutral solution always has $[H^+] = [OH^-]$, so $pH = pOH = pK_w / 2$. Adding $HCl$ introduces $H^+$, which shifts the water equilibrium backward (common ion effect).