In a dilute sodium bicarbonate solution, H+ =1.9*10^-8M. Without using a calculator, what integer value will this pH be near? Calculate the pH.

Answer 1

The pH of a solution is a measure of the molar concentration of hydrogen ions (H⁺) in the solution.

Mathematically: pH = -log₁₀[H⁺]

(As a reminder, based on the mathematics of logs, this means that [H⁺] = 10^-pH)

Basically, since the pH scale has 10 as its base, since [H⁺] ≈ 10^-8, the pH is about 8.

If you plug -log(1.9 x 10^-8) into your calculator, it will tell you the pH for this solution is more precisely 7.72. Why less than 8? Because the [H⁺] was slightly greater than 10^-8, meaning this solution is slightly more acidic than that (and low values on the pH scales correspond to more acidic solutions).