III.2 Titration the Ca(OH2 in distilled wateP lill ile of Titration Trial mL. mL
ID: 506303 • Letter: I
Question
III.2 Titration the Ca(OH2 in distilled wateP lill ile of Titration Trial mL. mL HCI (DIII.2c DIII.2b) b. [OH 1 (DIII.2a, AII.2c, and AIII.2a in eq. (3)) c. Solubility (S) (AIII.2b in eq. (11c) e. Std dev S d. Mean S 275M O.o2. (AIII.2c in eq. (14)) (AIII.2b in eq. (11d)) O sooooo 53 h. Std dev ksp O.OOOOISIO g. Mean Kisp (Ca(OH02) (AIII.2f in eq. (14)) (AII.2f, g in eq. (16)) IV.2 Titration the of Ca(OH)2 in 0.010 M Mg(NO3)2 filtrate Titration Trial Aria a. 6.68 mL mL HCI (DIV.2c DIV.2b) b. [OH o 2343 M O. a3el M (DIV.2a, AII.2c, and AIV.2a in eq. (3)) c. Solubility (S) 5 M (AIV.2b in eq. (11c)) d. Mean S e. Std dev S (AIV.2c in eq. (14)) (AIV.2c, d in eq. (1 V.2 Titration the of Ca(OH)2 in 0.010 M Ca(NO32 filtrate tration Trial 1 mL. mL a. Vi mL HCI (DV.2c DV.2b) 0.036 b. [OH (DV.2a, AII.2c, and AV.2a in eq. (13)) o ol Solubility (S) 543 (Av.2b in eq. (11c) e. Std dev S 0.018 us325 M d. Mean S (AV.2c, d in eq. (16) (AV.2c in eq (14)) 192Explanation / Answer
1. Unlike phenolphthalein indicator, bromocresol purple has a very fine pH range for the color change. the equivalence point of the titration here matches with the pH for the color change of bromocresol purple more closely than the pH change for higher phenolphthalein. Thus as the pH changes around 6 at the equivalence point for the given titration, the color of bromocreasol purple also changes accrodingly and is very accurate to be used for this acid-base titration.
2. The volume of HCl used, would be higher If some undissolved Ca(OH)2 is allowed to pass into the system. The added HCl would react with OH- in solution and would reduce the concentration of it in solution, which would shift the equilibrium to the side so that more of undissolved Ca(OH)2 dissolves in solution and prodces free OH- ions. The solubility results would thus be higher.
3. Substituting Mg(NO3)2 with Mg(CH3COO)2 is not a good choice as the conjugate acid formed here is a weak acid CH3COOH unlike conjugate acid formed in case of Mg(NO3)2 which is a strong acid HNO3. This would thus change the solubility of Ca(OH)2 and we would get different value at the end other than the expected result.
4. Yes, a filtered solution of Mg(OH)2 can be used to test the solubility of Mg(OH)2 in solution, came as we have done the solubility analysis for Ca(OH)2 in solution. In both the cases, the dissolved salt would be titrated and the volume of titrant used teslls us the amount of salt in solution and hence the solubility. Literature Ksp value of Mg(OH)2 is much lower than Ca(OH)2 so we would expect far less salt in solution.
5. the solubility of Ca(OH)2 decreases upon addition of common ion Ca(NO3)2 to the solution as the dissolved Ca2+ from Ca(NO3)2 would forces the equilibrium to shift towards reactant end and thus more of undissolved Ca(OH)2 would form in solution. Ca(OH)2(aq) <==> Ca2+(aq) + 2OH-(aq). This is according to th LeChatelier's principle. The solubility however was found to increae by the addiiton of an uncommon ion Mg(NO3)2 in solution due to salt effect increase of the resulting solution.