The purpose should include a majority of the topics and techniques covered in the experiment. The procedure section should cite the lab manual and include any changes made to the procedure during lab work.

The data section MUST include a balanced equation of the reaction being studied. A table should be made with the following for each temperature studied; a) the average  change in volume of your two trials (DV (mL) = V_Final - V_Inital), b) the hydroxide concentration [OH^-], c) the molar solubility, d) the K_sp and e) DG.

The hydroxide concentration [OH^-] can be found using the following method; the concentration of HCl should have been recorded in lab, use that value and the DV to find the moles of HCl. From the moles of HCl and the balanced equation, you can use the mole ratio to determine the moles of  OH^-. This is a simple stoichiometry problem like you have done several times previously. From the moles of OH- and volume that you titrated out (I.e. how much liquid did you put in your Erlenmeyer flask?) you can get the concentration of [OH^-]. Mathematically the problem would be set up like this:

Once you have the concentration of [OH-] you can get the molar solubility of the solid.

Molar Solubility of Ca(OH)₂= [OH^-]/2

Once the molar solubility is determined The K_sp at each temperature is determined by:

K_sp = [OH^-]^m[Ca²⁺]ⁿ  (n and m are found in your balanced chemical equation)

Note: the concentration of Ca²⁺ is equal to the molar solubility.

G for each temperature can be determined using DG=-RT ln K_sp, where R is the gas constant, T is temperature in Kelvin, K_sp is the equilibrium constant and DG is Gibbs free energy. Make sure you have the correct units. DH and DS for this reaction should also be stated and are determined from a graph (see calculations).

The calculation section should include a graph of DG vs temperature (in Kelvin) AND a graph of molar solubility vs temperature. All graphing guidelines apply. Example calculations of the following should also be included: sample Calculations for the following should also be included: [OH^-], molar solubility, K_sp, DG, DH, and DS. The values for DH and DS are determined from the free energy graph where the slope of the graph is –DS and the y-intercept of the graph is DH. Make sure that the units are correct in all of your calculations and answers.

The conclusion section should be in paragraph form and include the [OH^-], and Ca(OH)₂ molar solubility. The discussion of the solubility trend seen on your molar solubility vs. temperature graph should be explained. Another discussion should be included regarding the values, trends and discrepancies in the values for K_sp, DG, DH, and DS. Finally be sure to include possible errors.

Answer the following questions:

1. Why do you have to filter the Ca(OH)₂ solution before titrating it?

2. Why don't you have to accurately record the amount of Ca(OH)₂(s) used in the saturated solution?