Final answer:
Calcium hydroxide dissociates into calcium ions and hydroxide ions. The molarity of Ca2+ is 0.620 M, and the molarity of OH- is double that of Ca(OH)2 at 1.240 M. The total ion molarity would be 3.100 M, but this is not an available option.
Step-by-step explanation:
The question asks about the molarity of ions in a 0.620 M solution of Ca(OH)2.
Calcium hydroxide, Ca(OH)2, dissociates completely in water to form calcium ions (Ca2+) and hydroxide ions (OH-). The dissociation can be represented by the following equation:
Ca(OH)2 → Ca2+ + 2 OH-
For every 1 mole of Ca(OH)2 that dissolves, it produces 1 mole of Ca2+ ions and 2 moles of OH- ions. Therefore, the molarity of Ca2+ ions in the solution is the same as the initial molarity of Ca(OH)2, which is 0.620 M.
For OH- ions, since there are two per formula unit, the concentration is twice the molarity of Ca(OH)2. Thus, the molarity of OH- ions is:
OH- molarity = 2 × 0.620 M = 1.240 M
The sum of the molarities of the ions would be the concentration of Ca2+ plus twice the concentration of OH- because there are two hydroxide ions for every calcium ion. Therefore:
Total ion molarity = [Ca2+] + 2[OH-] = 0.620 M + (2 × 1.240 M) = 3.100 M
However, none of the provided answer options match this total ion molarity. The options only seem to refer to individual ion molarities, not the combined total.