Respuesta :
About 222 mV is generated by the pH gradient.
The Nernst equation determines the electrochemical cell potential at any given temperature, pressure, etc. It explains how cell potential relates to both the activities of electrically active (electroactive) species and standard potential.
The voltage generated across a membrane because of the hydrogen ion concentration gradient is [tex]E=\frac{2.303RT}{nF} \times\Delta pH[/tex]. Here, E is reduction potential, T is the temperature in kelvin, R is the universal gas constant, n is ion charge, and F is the Faraday constant.
Given, T=25°C=25+273=298K and pH=3.75. We know that, R=8.314J/mol.K and F=96485J/V.mol.
Then,
[tex]\begin{aligned}E&=\left(\frac{2.303\times8.314\times298}{1\times96485}\right)\times3.75\\&=0.0591\times3.75\\&=0.2216\\&=\mathrm{0.222\;V}\\&\approx\mathrm{222\;mV}\end{aligned}[/tex]
The answer is 222 mV. Therefore, the correct option is B.
The complete question is -
When the difference in pH across the membrane of a glass electrode at 25 °C is 3.75 pH units, how much voltage is generated by the pH gradient?
A. Not Enough Information to Determine
B. 222 mV
C. 180 mV
D. 273 mV
E. 0.222 mV
F. 0.273 mV
G. 3.75 mV
To know more about the Nernst equation:
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