ρ -Functions

Scientists frequently express the concentration of a species in terms of its ρ-function, or ρ-value. The ρ-value is the negative logarithm (to the base 10) of the molar concentration of that species. Thus, for the species X,

ρX = -log [X]

As shown by the following examples, ρ-values offer the advantage of allowing concentrations that vary over ten or more orders of magnitude to be expressed in terms of small positive numbers.

Example : Calculate the p-value for each ion in a solution that is 2.00 x 10^-3 M in NaCl and 5.4 x 10^-4 M in HCl.

Solution