Question

(a) When the difference in pH across the membrane of a glass electrode at is 4.63 pH units, how much voltage is generated by the pH gradient?

(b) What would the voltage be for the same pH difference at 37 degrees celcius?

Answer 1

a) Voltage generated by the pH gradient across the membrane of glass electorde can be calculated by the formula: (2.303RT*ΔpH)/nF

where,

R (gas constant) = 8.314 J/K/mole
T (temperature in kelvin) = 25 + 273.15 = 298.15 K
n= 1
F (Faraday's constant)= 96485.33

ΔpH (difference in pH) =4.63

Voltage generated = (2.303*8.314*298.15*4.63)/(1*96485.33) = 0.2739 V = 273.9 mV

b) No. It will not be same at 37 degree celsius.

T= 37 + 273.15 = 310.15 K

Voltage generated = (2.303*8.314*310.15*4.63)/(1*96485.33) = 0.2850 V = 285 mV