30. Solving a chemistry problem

48. To assess the interfering effect of sodium in the determination of potassium ions using an ion-selective electrode based on valinomycin, the mixed solution method was used. All solutions for constructing a calibration curve for potassium contained 140 mm sodium ion. The coordinates of the point of intersection of the linear sections of the obtained dependence: E=17.4 mV, the concentration of potassium ion 1.5*10-5 M. The tangent of the angle of the electrode function is 57.8 mV. What is the value of kK /Na for this electrode? Answer: 1.07 * 10-4