Question

from the following data, which were obtained in the 100 ml photometric titration of a solution of KMnO4 with H2C2O4 (0.01M). Determine the concentration of the permanganate solution and its molar absorptivity if the cell used was one centimeter thick and the reaction is as follows: 2MNO4^- + 5C2O4^2- + 16H⁺ → 2Mn²⁺ + 10CO2 + 8H2O

titrant (ml)	absorptivity	titrant (ml)	absorptivity
0.0	1.430	2.75	0.350
0.50	1.210	3.00	0.270
0.75	1.100	3.25	0.180
1.00	1.030	3.50	0.090
1.50	0.820	3.75	0.040
1.75	0.710	4.00	0.020
2.00	0.600	4.25	0.010
2.25	0.510	4.50	0.000
2.50	0.430	4.75	0.000

Answer 1

The titrant volume at the equivalence point is 4.5 mL, the solution concentration is calculated:

C MnO4- = 5 * Ca * Va / 2 * V MnO4- = 5 * 0.01 M * 4.5 mL / 2 * 100 mL = 0.0011 M

Molar absorptivity is the first read of the KMnO4 solution: 1.430.

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