Blood has a pH of 7.3. What is its hydronium ion concentration?

1. From the definition of pH, the logarithm of the hydronium molarity is minus 7.3. 2. So the molarity is ten raised to the power minus 7.3. 3. Split the exponent: ten to the minus 8 multiplied by ten to the power 0.7. 4. Ten to the power 0.7 is about 5, so the molarity is about 5 x 10^-8. 5. So the hydronium concentration is 5 x 10^-8 mol per litre, slightly alkaline. 6. Reading 7.3 straight into the coefficient is the trap that gives 7.3 x 10^-7. _Source: OpenStax Chemistry (CC BY 4.0), Ch 14 "Acid-Base Equilibria", section 14.2 pH and pOH_