Question

Calculate the concentrations for the values with an asterisk beside them.

Solution: Potential: 10-4M 26 mV 10-2M 68 mV 10-3M 111 mV 10-4M 163 mV 10-SM 210 mV 10-M 254 mV Unexpired (Beginning of Tube) 107 mV* Unexpired (End of Tube) 108 mV* Expired (Beginning of Tube) 104 mV* Expired (End of Tube) 112 mV*

Answer 1

It is clearly observed that the concentration and Potential have a logarithmic relation between them. Hence we can use interpolation between points to solve it.

$\frac{107 - 68}{x + 2} = \frac{111-68}{-3+2}$

x = -2.093

Concentarion = 10^x = 0.00807 M

Similarly for the rest,

108mV : Concentration = 0.0085159 M

104mV : Concentration = 0.006874 M

112mV: Concentration = 0.001 M