Final answer:
The hydronium ion concentration in a 0.01 M solution of Ca(OH)2 is 5 × 10¹³ M, calculated using the water dissociation constant.
Step-by-step explanation:
The concentration of hydronium ion in a solution can be determined if you know the concentration of hydroxide ions and vice versa, thanks to the water dissociation constant (Kw) at 25 °C, which is 1.0 × 10-14 M2. For a solution of 0.01 M Ca(OH)2, which is a strong base, it will dissociate completely in water providing 0.02 M OH- ions (since each Ca(OH)2 gives two hydroxide ions).
To find the hydronium concentration, use the formula Kw = [H3O+][OH-]. Rearranging this for [H3O+], we get [H3O+] = Kw / [OH-] = 1.0 × 10-14 M2 / 0.02 M, which equals 5 × 10-13 M. Therefore, the concentration of hydronium ion is 5 × 10-13 M.