The formula of the complex MXn can be determined by the mole-ratio method. Solutions are prepared in which the concentration of M is held constant and that of X is varied. The absorbance of the complex is measured.
The following data were obtained by mixing solutions A, 0.0100 molar in M, solution B, 0.01200 molar in X, and solution C, 0.100 molar in HClO4.
mL A mL B mL C Absorbance
4 0 16 0
4 1 15 0.125
4 3 13 0.375
4 4 12 0.5
4 5 11 0.625
4 6 10 0.75
4 10 6 1
4 12 4 1
Plot the absorbance against the ration of moles of X to moles of M. Calculate the formula of the complex from the mole ratio at which the absorbance reaches a maximum and levels off.