Transcript The common ion effect Saturated sodium chloride solution contains solid NaCl in equilibrium with the aqueous ions: NaCl(s) Na+(aq) + Cl–(aq) We know this sodium chloride solution is.

The common ion effect
Saturated sodium
chloride solution contains
solid NaCl in equilibrium
with the aqueous ions:
NaCl(s)
Na+(aq) + Cl–(aq)
We know this sodium
chloride solution is saturated
because there are crystals
of solid NaCl at the bottom
of the bottle.
Some of the saturated
solution is poured into a
test tube.
Since this liquid is clear
we know that all the ions
are in solution.
Concentrated hydrochloric acid
contains a high concentration of
Cl–(aq).
Some of the colourless conc
HCl solution is put in a
dropper, ready to add to the
saturated salt solution.
A single drop of HCl falls
into the saturated solution
and immediately forms
crystals of NaCl.
It’s more impressive if we
give it a good squirt…
Saturated NaCl contains about 6 mol L–1 of NaCl.
[Na+] = 6 mol L–1; [Cl–] = 6 mol L–1
[Na+][Cl–] = Ks = 36
Concentrated HCl is about 11 mol L–1, which significantly
increases the concentration of chloride ions.
Since the ionic product, [Na+][Cl–], exceeds the Ks, a
precipitate of NaCl(s) forms.
The solubility of a compound will decrease in the
presence of another compound with a common ion.
You may have separated soap (sodium stearate) from the
mixture of glycerol and unreacted sodium hydroxide by
adding saturated salt.