Question

Calculated values of n and formulas of Ni2+ complexes present in solution.

Z+nL <-> ZL_n

Z=Ni2+ L=en

Experiment on Complex ion composition by the continuous variation method

100mL of each 0.4M NiSO4· 6H2O and 0.4 M ethylenediamine was prepared, Prepare mixtures of the above solutions having a total volume of 10 mL, in which the mole fraction of ethylenediamine, X, is 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9.

Answer 1

First of all, determine the absorbances of each of these solutions and of the pure 0.4M nickel sulphate at the following wavelengths: 530, 545, 578, 622 and 640цm.

Now, calculate Y values (use following equation) at each wavelength for all solutions and make a plot of Y vs X for each of the above wavelengths.

Y = A_meas- (1-X) A_Z .............................(1)

Where A_Zis the absorbance of the pure M molar Ni²⁺solution,

A_meas is the measured absorbance

X is the mole fraction of ethylenediamine

From the value of X at each of the five maxima the values of n for the [Ni(en)₂]²⁺ complexes can be calculated from following equation.

n = X /(1-X) .....................(2)