For a lab I had to determine the solubility and Ksp of Ca(OH)X2 by performing two different titrations. I am given the formula to find solubility in molarity it is as written below.
Solubility of Ca(OH)X2 in molarity=Moles of soluteVolume of solution
I know the moles of solute, which is Ca(OH)X2, from calculations: 0.0001664 moles. The only question I have is what volume do I use? I tried using the volume of Ca(OH)X2 used, 0.01 L, which gave a result of 0.01664 M. This closer to the literature value of 0.0216 M than my second method. Second method I used the volume of the entire solution at the end of the titration, 0.03020 L, which resulted in a solubility of 0.005510 M. My question is if either of these methods are correct? If not, could you please point me in the right direction?
Thanks for helping!!
P.S. Sorry I'm not very good with formatting and computers and I don't know how to edit my equations to look pretty or very clear
Information:
Amount of Ca(OH)X2 added: 10.00 mL
Amount of HCl added: 20.20 mL, concentration of 0.01647 M
Steps:
1) Find amount of HCl added to Ca(OH)X2 and indicator.
Volume of HCl added = 20.20 mL, molarity of HCl = 0.01647 M, moles of HCl added= 0.0003327
*Since the competing equilibrium of the strong base, calcium hydroxide, and the strong acid, HCl, cancel out the only equilibrium left is water. So the amount of HCl added will be proportional to the amount of HX3OX+ and OHX−.
2) Find molarity of OHX− and CaX2+ ions
Molarity of OHX− = 0.0003327 moles0.01000 L=0.03327 M
Molarity of CaX2+ is equal to 0.5 OHX− because the chemical equation of the dissociation of Ca(OH)X2−⇀↽−CaX2++2OHX−
3) Find Ksp. Ksp=[CaX2+][OHX−]=[0.01664][0.03327]2=1.842⋅10−5 4) Find solubility of Ca(OH)X2 in molarity
Solubility in Molarity= moles of solute/ volume of solution solubility=0.0001664/0.03020L solubility= 0.005510M OR solubility=0.0001664/0.01000L solubility= 0.01664M
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