Final answer:
The hydroxide ion concentration of a lye solution with a pH of 11.20 is 1.6 x 10-3 M.
Step-by-step explanation:
The hydroxide ion concentration of a lye solution that has a pH of 11.20 can be calculated using the relationship between pH and pOH as well as the ion product constant of water (Kw) at 25 °C, which is 1.0 x 10-14. First, calculate the pOH of the solution using the formula pOH = 14 - pH. For a pH of 11.20, pOH = 14 - 11.20 = 2.80. Then, to find the hydroxide ion concentration, use the formula [OH-] = 10-pOH, which gives [OH-] = 10-2.80 = 1.6 x 10-3 M.