Calibration of a glass electrode gave a reading of 146.3 mV with saturated potassium hydrogen tartrate buffer standard (pH = 3.557) and a reading of -81.9 mV with 0.008695 potassium dihydrogen phosphate, 0.0343 m disodium hydrogen phosphate buffer standard (pH = 7.400), both measured at 30°C.
(a) What is the observed slope (mV/pH unit) of the calibration curve?
(b) What is the theoretical slope at 30°C?
(c) What is ?, the electromotive efficiency to three significant figures?? Open the hint panel below for the definition of electromotive efficiency.
(d) What is the pH of an unknown that gives a reading of 19.6 mV with this electrode at 30°C?