One of the issues caused by acid rain is the lowering of pH of small lakes, which leads to the death of numerous aquatic fish and plant species. Calcium oxide, commonly known as lime, is frequently used to temporarily remediate lakes that have been acidified by acid rain. Suppose you are tasked with restoring an acid lake with a volume of 3.00 × 1010𝐿 and a pH of 5.0. Using the equilibria below, what mass of calcium oxide will be needed to restore the lake to an ideal pH of 6.5?

Question

𝐶𝑎𝑂(𝑠) + 𝐻2𝑂(𝑙) ↔ 𝐶𝑎(𝑂𝐻)2(𝑠)

𝐾𝑒𝑞 = 1.33 × 1010

𝐶𝑎(𝑂𝐻)2(𝑠) ↔ 𝐶𝑎2+(𝑎𝑞) + 2𝑂𝐻−(𝑎𝑞)

𝐾𝑠𝑝 = 5.61 × 10−5

Answer 1

How much OH in pH=5 and How much OH in pH=6.5. Determine difference and that's how much CaO is needed.