Calcium hydroxide has Ksp = 5.5 x 10-5 at 25 oC and a molar mass of 74.10 g/mol.
How many grams of calcium hydroxide are needed to create 365 mL of a saturated solution of calcium hydroxide at 25 oC?
....Ca(OH)2(s) ==> Ca^2+(aq) + 2OH^-(aq)
I...solid...........0...........0
C...-x..............x..........2x
E..solid-x..........x..........2x
Substitute the E line (ignore the solid-x since we don't include solids in Ksp) into Ksp expression and solve for x = solubility Ca(OH)2 in mols/L = M.
Then convert M to mols (mols = M x L) and convert to grams (g = mols x molar mass). That will be g necessry to prepare 365 mL of a saturated Ca(OH)2 solution.
To determine the number of grams of calcium hydroxide needed to create a saturated solution, we need to use the formula:
Ksp = [Ca2+][OH-]^2
Where:
Ksp = solubility product constant
[Ca2+] = concentration of calcium ions in mol/L
[OH-] = concentration of hydroxide ions in mol/L
Since calcium hydroxide dissociates into one calcium ion (Ca2+) and two hydroxide ions (OH-), we can consider the molar solubility of calcium hydroxide as x mol/L.
Therefore, the concentration of calcium ions ([Ca2+]) will also be x mol/L, and the concentration of hydroxide ions ([OH-]) will be 2x mol/L.
Using the given Ksp value, we can write:
5.5 x 10^(-5) = x * (2x)^2
5.5 x 10^(-5) = 4x^3
Solving this equation for x will give us the molar solubility of calcium hydroxide.
x = ∛(5.5 x 10^(-5) / 4)
Now, we can calculate the number of moles of calcium hydroxide (Ca(OH)2) required to create a saturated solution in the given volume of 365 mL.
Moles of Ca(OH)2 = molar solubility (x) * volume (in liters)
Moles of Ca(OH)2 = x * 0.365 L
Finally, we can calculate the mass of calcium hydroxide required using the molar mass:
Mass of Ca(OH)2 = Moles of Ca(OH)2 * Molar mass
Substituting the values and calculating will give us the answer:
Mass of Ca(OH)2 = (x * 0.365 L) * 74.10 g/mol