The ion product of water at 80 degrees Celsius is 2.4 x 10^-13. What is the hydronium concentration in pure water there?

1. Pure water still makes the two ions in equal numbers at any temperature. 2. So the ion product equals the hydronium concentration multiplied by itself. 3. That means the hydronium concentration is the square root of 2.4 x 10^-13. 4. Rewrite the constant as 24 x 10^-14 so the exponent is even and easy to halve. 5. The square root of 24 is 4.9 and the square root of 10^-14 is 10^-7. 6. So the hydronium concentration is 4.9 x 10^-7 mol per litre. 7. Quoting 1.2 x 10^-13 is the trap of halving the constant instead of taking its root. 8. The familiar 1.0 x 10^-7 applies only at 25 degrees Celsius, not at 80. _Source: OpenStax Chemistry (CC BY 4.0), Ch 14 "Acid-Base Equilibria", section 14.1 Brønsted-Lowry Acids and Bases_