The number of hydronium ions in 1 ml of an aqueous solution of pH 12.0 at 25°C is — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

A pH of 12.0 means $[\text{H}_3\text{O}^+] = 10^{-12}\text{ M}$. In 1 ml ($10^{-3}\text{ L}$) of this solution, the number of moles of hydronium ions is $10^{-12}\text{ mol/L} \times 10^{-3}\text{ L} = 10^{-15}\text{ moles}$. To find the number of individual ions, multiply by Avogadro's number ($N_A \approx 6.02 \times 10^{23}$): $10^{-15} \times 6.02 \times 10^{23} = 6.02 \times 10^8$ ions.