Question

Discussion. Explain whether each of the errors below would cause your calculated Ksp value to be higher or lower than the tabulated value. Assume you are using method 1 to calculate Ksp. It is also possible that the error would have no effect on the measured Ksp value (so it really wouldn’t be an error). (1 point each)

1. The calcium hydroxide solution was prepared at the last minute. Adequate time was not given for equilibrium to be reached between the solid and dissolved calcium hydroxide. (These solutions are prepared by adding solid calcium hydroxide to DI water and stirring it for a long time.)

2. The burette was not rinsed with 10 mL of HCl and HCl was not run through the stopcock before it was filled with acid. Some DI water, therefore, remained on the sides of the burette and in the stopcock.

3. The pH meter was not calibrated before the experiment. All the pH readings were 0.2 pH units too high.

4. The HCl was not diluted correctly. Although it was labeled 0.020 M, it was really 0.030 M.

Answer 1

Q1

if there is not plenty of Ca+2 and Oh- in solution

the Ksp data will be LOWER than the real one, therefore

Ksp will be lower

Q2

The solution of HCl is much more concentrated, so it will require less volume, which implies less moles of HCl

HCl is related to OH- which is directly proporitonal to Ksp

therefore, it lowers

Q3

pH = relates to pOH

pOH = -log([OH-])

then

if pH is higher, then pOH is lower

which imploes higher [OH-]

that is, hihger Ksp data

Q4

if HCl has higher moalrity, then the molarity calcualted of OH- will be lower

which implies lower Ksp since [OH-] relates directly