Calculate the Ksp Ca(OH)2 25cm3 of a saturated solution required 11.45cm3 of 0.1mol/dm3 HCl for neutralization.
2HCl + Ca(OH)2 --> CaCl2 + 2H2O
1 dm^3 = 1L
moles HCl used = M x L.
Look at the coefficients in the balanced equation. That many moles HCl means 1/2 that for moles Ca(OH)2.
That is the # moles Ca(OH)2 in 25 cc. Convert that to moles in 1 dm^3 (1L) solution. Let's call that S for solubility. Then
Ca(OH)2 ==> Ca^+2 + 2OH^-
...S.........S.......2S
Substitute the value of S (or 2S) into the Ksp expression and solve for Ksp. Post your work if you get stuck.
Ksp = (Ca^+2)(OH^-)^2
To calculate the Ksp (solubility product constant) of Ca(OH)2, we need to know the concentration of OH^− ions in the saturated solution. We can determine this by using the neutralization reaction between Ca(OH)2 and HCl.
The equation for the neutralization of Ca(OH)2 with HCl is:
Ca(OH)2 + 2HCl -> CaCl2 + 2H2O
We know that the molar ratio between Ca(OH)2 and HCl is 1:2. So, the moles of Ca(OH)2 can be calculated using the following formula:
moles of Ca(OH)2 = concentration of HCl x volume of HCl used / 2
Given that the concentration of HCl is 0.1 mol/dm^3 and the volume of HCl used is 11.45 cm^3, we need to convert the volume to dm^3:
volume of HCl used = 11.45 cm^3 = 11.45 / 1000 dm^3 = 0.01145 dm^3
Now, we can calculate the moles of Ca(OH)2:
moles of Ca(OH)2 = 0.1 mol/dm^3 x 0.01145 dm^3 / 2 = 0.0005725 mol
Since 1 mole of Ca(OH)2 produces 2 moles of OH^− ions, we can determine the moles of OH^− ions:
moles of OH^- = 2 x moles of Ca(OH)2 = 2 x 0.0005725 mol = 0.001145 mol
Finally, we can calculate the concentration of OH^- ions in the saturated solution:
concentration of OH^- = moles of OH^- / volume of solution
The volume of the solution is given as 25 cm^3, so we need to convert it to dm^3:
volume of solution = 25 cm^3 = 25 / 1000 dm^3 = 0.025 dm^3
Now we can calculate the concentration of OH^- ions:
concentration of OH^- = 0.001145 mol / 0.025 dm^3 = 0.0458 mol/dm^3
The Ksp (solubility product constant) of Ca(OH)2 can be determined using the equation:
Ksp = [Ca^2+][OH^-]^2
Since the concentration of Ca^2+ ions is equal to the concentration of OH^- ions in a saturated Ca(OH)2 solution, the Ksp can be calculated as:
Ksp = (0.0458 mol/dm^3)(0.0458 mol/dm^3)^2 = 0.0953 mol^3/dm^9
Thus, the Ksp of Ca(OH)2 is approximately 0.0953 mol^3/dm^9.