Conductivity measurements were one of the first methods used to determine the autoionization constant of water. The autoionization constant of water is given by the following equation:

where a is the activity of the species, which is equal to the actual concentration of the species divided by the standard state concentration at infinite dilution. This substitution of concentrations for activities is a reasonable approximation

given the small concentrations of H⁺ and OH^ˆ’ that result from autoionization.

a. Using the expression provided, show that the conductivity of pure water can be written as

b. Kohlrausch and Heydweiller measured the conductivity of water in 1894 and determined that Λm (H₂O) = 5.5 × 10^-6 S m^-1 at 298 K. Using the information provided in Table 34.2, determine K_w.

Transcribed Image Text:

[н] (он ] ад аон 1м K. 1м A,(H,0) = (1 M)K,²(A(H*)+ A(OH-).