At 90°C, the hydronium ion concentration in pure water is . If 100 ml of solution is mixed with 250 — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

In pure water at 90°C, $[\text{H}^+] = 10^{-6}\text{ M}$, so $K_w = 10^{-12}$. Moles of NaOH = $100\text{ ml} \times 0.5\text{ M} = 50\text{ mmol}$. Moles of $\text{HNO}_3$ = $250\text{ ml} \times 0.2\text{ M} = 50\text{ mmol}$. The strong acid and strong base are present in stoichiometrically exact amounts, neutralizing each other completely to form a neutral solution of $\text{NaNO}_3$. A chemically neutral solution at 90°C has $[\text{H}^+] = \sqrt{K_w} = 10^{-6}\text{ M}$, yielding a pH of 6.0.