43. Solution to Chemistry Problem

3. In standard solutions of potassium salt with concentration СК+, the electrode potentials of the potassium-selective electrode relative to the silver chloride electrode were measured and the following data were obtained:
СК+, mol∙L–1 1.0∙10–1 1.0∙10–2 1.0∙10–3 1.0∙10–4
E, mV 100 46.0 – 7.00 – 60.0

Based on these data, plot a calibration graph in coordinates E – рСК+.
A 0.2000 g sample containing potassium was dissolved in water, and the volume was brought to V (ml). Then the electrode potential of the potassium-selective electrode Ех was measured in the resulting solution:
Calculate the mass fraction of potassium w (%) in the sample.

Option 3
V, ml 250
Ex, mV 10.0