The following tables organize the values that need to be collected during the course of the experiment.
T29.1 Titration Measurements
mass of ZnSO4 used
2. 874g
mass of (NH4)2C204 used
1.421g
Molarity of KMnO4 provided
trial 1
trial 2
0. 00
ML
trial 3
trial 4
Vini
Vfin
0. 00mL
15.50mL
0•00 mL
21•04 mL
0.00 mL
14.80 mL
0•00 mL
25.20 mL
Calculations
Using the experimental data, students can determine the Ksp value for the zinc oxalate that they formed during the first lab period.
T29.2 Ksp Determination of ZnC204
trial 1
trial 2
trial 3
trial 4
VMnO4
L
L
L
L
nc2O4
mol
mol
mol
mol
Пс204
mol
mol
mol
mol
Мс204
M
M
M
M
Ksp
Average Ksp
Volume of permanganate dispensed, Mno4
This value is the difference between initial and final volume readings taken from the buret.
This value
should then be converted into the standard unit of volume: liters.
Moles of permanganate dispensed, molMno
This value is found by multiplying the volume of permanganate dispensed, 'VMos' by the molarity of KnO4 provided by the stockroom.
Moles of oxalate reacted, Nc204
At the equivalence point, the moles of permanganate dispensed have completely reacted with the moles of oxalate present in the Erlenmeyer flask. The ratio of moles between the two reactants can be verified by balancing the redox equation associated with the titration.
Molarity of oxalate in solution, Mc204
This value gives the oxalate concentration in the supernatant liquid that was decanted into the Erlenmeyer flask. The molarity is found by taking the moles of oxalate that reacted and dividing by the volume of oxalate solution that was decanted for each trial.
Ksp of zinc oxalate, Ksp
Since zinc oxalate solid does not appear in the equilibrium constant expression, all that is needed to calculate the Ksp is the free oxalate and zinc ion concentrations present in the supernatant liquid.
Stoichiometrically, the zinc concentration should be identical to that of oxalate, whose concentration is determined by the titration. Therefore, the Ksp should be equal to double the molarity of oxalate, 'Mczos' raised to the second power.
