What does it mean for a substance to
be insoluble in water?
–It will not dissolve in water, that it will precipitate out
of a solution if it is one of the
products in a reaction.
–That is, PbCl2 (s) + H2O(l) ® No change!
And therefore,
2NaCl(aq) + Pb(NO3)2 (aq) ® PbCl2 (s) + 2NaNO3 (aq)
ppt.
PbCl2 precipitates out of
the solution since it is an insoluble compound (check solubility rules).
Similarly, Ba(NO3)2 (aq) + K2CrO4 (aq) ® BaCrO4 (s) + 2 KNO3 (aq)
ppt.