# How does molar conductivity relate to the salinity of a solution?

##### 1 Answer

In general, it is not easy to say... At *very low concentrations* (below *linear*).

But at "usual" concentrations, I believe the influence of the salinity (salt concentration) **tapers off due to increased ion pairing**, decreasing the effective number of ions in solution and thus the conductivity.

In that case it may be more of a *square root*, or even *logarithmic* direct proportionality as concentrations get beyond

Well, salinity of water is a type of concentration. It is commonly given as:

#"g salt"/"kg sea water"#

And so, it is proportional to the molar concentration, in

If we define that as **molar conductivity** is given for low concentrations (less than

#Lambda_m = Lambda_m^(oo) - (A + BLambda_m^(oo))sqrtc# where:

#Lambda_m# is themolar conductivityin#"S"cdot"m"^2cdot"mol"^(-1)# .#Lambda_m^(oo)# is the molar conductivity in thelimit of infinite dilution. This is obtained by extrapolating a tangent line on a#Lambda_m# vs.#c# graph to a theoretical#Lambda_m# at#c ~~ 0# .#A# and#B# are constants from the Debye-Huckel theory of electrolytes. For further detail on how to calculate#A# and#B# , see here.

As

However, this relationship is muddled at higher concentrations, due to ion pairing occurring at higher concentrations, decreasing the influence of concentration on conductivity.