Procedure solution of Co(OH) H solution in a small Part 1: Make a saturated solu

Question

Procedure solution of Co(OH) H solution in a small Part 1: Make a saturated solution graduated cylinder annd pour Measure 10 mL of 0.3 M KOH in a 10 mL 0.5 g of CaCl, and add the solid to the NaOH solution and swirl the flask to mix wel FOH beaker. Measure 0.5 Be sure to record the exact mass of cacl, used. Allow the miature to sit for at least 5 minutes before flask, and filter paper. Turn cfunnel, sidearm flask, and filter paper filtering on the vacuum, DO NOT wet the filter paper then very carefully, slowly pour funnel. After the solution has filtered, turn off the vacuum, remove the funnel from the vacuum flask and pour the filtered liquid (filtrate) into a separate beaker (it is ok if the filtrate is a little clowdy). Labe this beaker and set um flask Ca t aside for pH determination. Replace the funnel on the vacuum flask, turn on the of Di water vacuum and use a sma solid CalOHl- in the funnet Here we are trying to wash away any loosely bound hydroxide ions from the calcium hydroxide. Turn off the vacuum. Carefully remove the filter paper from the Buchner funnel. paper and into the water. The filter paper may be to the beaker of water containing the solid Ca(OH) and place the beaker on a stir pl for at least 15 min. In order to have a saturated solution, t (meaning it did not all dissolve). Using a spatula, scrape the solid off the filter ining the solid Ca(OH)2 and place the beaker on a stir plate, Stir the mixture thrown in the regular trash. Add a magnetic stir bar here MUST be solid left in the solution Part 2: Determination of the pH Use a pH meter to determine the pH of the initial filtrate and the saturated Ca(OH)a solution. Calculation of Kp We will use two different methods to calculate K for Ca(OH)2: 1. Filtrate: Using the mass of calcium chloride used and a total volume of 10 ml, calculate the initial concentration of calcium ions in solution before the synthesis reaction. Use the pH of the filtrate solution to calculate the concentration of hydroxide ions in solution after the synthesis reaction. Use this information along with the initial concentration of hydroxide ions to construct an ICE table of the synthesis reaction. Use the equilibrium concentrations of Ca and OH to calculate K 2. Saturated Ca(OH)2 solution: Use the pH of the saturated solution to calculate the concentration of hydroxide ions in the saturated solution. Create an ICE table using the Ca(OH)2 dissociation reaction. Use the equilibrium concentrations of Ca and OH to calculate K

Explanation / Answer

Given data:

Mass of Cacl2 = 0.51g

NaOH used = 10ml

Molarity of NaOH = 0.3M

Saturated solution pH = 12.13

Solution:

The chemical equation: Ca(OH)2 Ca2+ + 2OH¯

The Ksp expression: Ksp = [Ca2+] [OH¯]2

Use the pH to get the pOH:   14.00 - 12.13 = 1.78

Use the pOH to get the [OH¯]:

[OH¯] = 10¯pOH = 10¯1.78 = 2.5042 x 10¯2 M

From the chemical equation, we note that the [Ca2+] is half the value of the [OH¯], therefore:

[Ca2+] = 2.5042 x 10¯2 M divided by 2 = 1.2521 x 10¯4 M

Now we have the necessary values to put into the Ksp expression:

Ksp = (2.5042 x 10¯2) (1.2521 x 10¯4)2

Ksp = 3.1355 x 10¯10.

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