Answer to Question #204125 in General Chemistry for Jc456

Question

Air-saturated water has a hydronium ion concentration caused by the dissolved CO₂ of 2.0 × 10^–6 M, about 20-times larger than that of pure water. Calculate the pH of the solution at 25 °C.

Answer 1

Concentration of the hydronium ions caused by the dissolved CO₂=2 .0×10^-6M

Concentration of hydronium in pure water = 2.0×10^-6$\div$ 20

=1.0×10^-7M

Therefore, Total concentration of hydronium ions=(2.0×10^-6+1.0×10^-7)M

=1.0×10^-7(20+1)M

=21×10^-7M

=2.1×10^-6M

$\therefore$ pH=-log[H₃O⁺]=-log(2.1×10^-6)

=5.68

pH of the solution at 25 °C is 5.68