Saturated solution of Ca(OH)2 in 0.05349 mol/L NaOH.
Temperature: 22.1 * C
Volume of Ca(OH)2/NaOH aliquot: 25ml
Concentration of Standard HCl: 0.1213M
Indicator Used: Bromothymol Blue
Ksp from previous part I got 3.55x10^-5
- Average volume of HCl added to titrate was 15.05 mL-
Question:
1.Calculate the total [OH ] in the saturated solution of Ca(OH)2 in sodium hydroxide for the -
solution assigned to you.
2. Calculate the [OH ] that comes from the dissolution of Ca(OH)2. The total [OH ] (calculated - -
above) is the sum of the [OH ] from the NaOH and the [OH ] from Ca(OH)2.
just to clarify,The ksp was for Ca(OH)2.
I don't remember the former post but I think you said to #1, "do I just calculate this from the HCl" and the answer is yes. My assumption is that you used the saturated soln of Ca(OH)2 but it had no solid in it that was titrated.
Total millimols OH^- = mL HCl x M HCl = 15.05 x 0.1213 = approx 1.83 but you need to do it more accurately. Then M = mmols/mL to get the total (OH^-) in mols/L.
#2. mmols NaOH at the beginning is mL x M = 25 x 0.05349 = about 1.41 but again you need a more accurate answer. Then (OH^-) from Ca(OH)2 in the sat'd solution is
total mols OH - mmols NaOH = mmols OH from the Ca(OH)2. Finally, M = mmols/mL.
Thanks a loooooooooot for help !!!! :D
Btw, from this how would we find the ksp and the solubility of CaOH2 in the naoh solution?
To calculate the total [OH-] in the saturated solution of Ca(OH)2 in sodium hydroxide, we need to consider the [OH-] from both NaOH and Ca(OH)2.
1. Calculate the [OH-] from NaOH:
Given concentration of NaOH = 0.05349 mol/L
The molar ratio between NaOH and OH- is 1:1, so the [OH-] from NaOH is also 0.05349 mol/L.
2. Calculate the [OH-] from Ca(OH)2:
To calculate the [OH-] from Ca(OH)2, we need to consider the Ksp (solubility product constant) and the stoichiometry of the reaction.
The balanced equation for the dissolution of Ca(OH)2 is:
Ca(OH)2(s) ⇌ Ca2+(aq) + 2OH-(aq)
From the equation, we can see that 1 mol of Ca(OH)2 produces 2 mol of OH-. Therefore, the concentration of OH- from Ca(OH)2 will be twice the concentration of Ca(OH)2 that has dissolved.
We can use the Ksp value and the solubility equation to calculate the concentration of Ca2+ ions:
Ksp = [Ca2+][OH-]^2
Rearranging the equation gives:
[OH-] = √(Ksp/[Ca2+])
Substituting the given Ksp value:
[OH-] = √(3.55x10^-5 mol^3/L^3) / [Ca2+]
Since the concentration of Ca2+ is not given, we cannot calculate the exact [OH-] from Ca(OH)2 without more information.