If the ionization constant of water, kw, at 40°c is 2.92 * 10-14, then what is the hydronium ion concentration and ph for an acidic solution?

Answer is: the hydronium ion concentratio is 1.71*10⁻⁷ mol/dm³ and pH<6.76.

The Kw (the ionization constant of water) at 40°C is 2.94*10⁻¹⁴ mol²/dm⁶ or 2.94*10⁻¹⁴ M².

Kw = [H₃O⁺] · [OH⁻].

[H₃O⁺] = [OH⁻] = x.

Kw = x².

x = √Kw.

x = √2.94*10⁻¹⁴ M².

x = [H₃O⁺] = 1.71*10⁻⁷ M; concentration of hydronium ion.

pH = - log[H₃O⁺].

pH = - log (1.71*10⁻⁷ M).

pH = 6.76.

pH (potential of hydrogen) is a numeric scale used to specify the acidity or basicity an aqueous solution.

The formula for Kw is:

Kw = [H+] [OH-]

For water, [H+] = [OH-]

Therefore we can write

Kw = [H+]²

For the temperature (40C) given,

Kw = 2.92 x 10^-14

[H+]² = 2.92 x 10^-14

[H+] = √ (2.92 x 10^-14)

[H+] = 1.71 x 10^-7

To determine the pH:

pH = - log [H+]

pH = - log (1.71 x 10^-7)

pH = 6.76