Lecture notes: CHEM103 – October 30, 2008
Ionic compounds conduct electricity: NOT as solids, but EITHER in solutions (below) or as liquids (not shown).
The difference between liquid salts (high melting points, see above) and solutions is the presence of a solvent (H2O).
(and the interations between the solvent and the solute…)
What liquid salts and aqueous ionic solutions have in common is MOBILE ions; the ability to MOVE charge!
SO – there is an analogy to be made between MELTING a salt to produce MOBILE ions, NOT in a lattice.
AND DISSOLVING a salt to produce MOBILE ions, but now SOLVATED, and also NOT in a lattice.
BOTH must overcome the lattice energy holding a solid ionic compound together!
Ionic Compounds in Solution
DEFINE: DISSOLUTION & PRECIPITATION…
WHY DO IONIC COMPOUNDS DISSOLVE AT ALL???
Back to lattice energy…
ENERGY OF SOLVATION VS LATTICE ENERGY… THIS IS A COMPETITION!!!
SO WHAT DO WE DO INSTEAD???
barium sulfate; mercury (II) chloride; copper (I) acetate, zinc (II) perchlorate, sodium phosphate, calcium phosphate
(when writing precipitation & dissolution reactions – note: do NOT include water!)
NOTE: partially soluble salts – what do these look like in solution at the atomic scale???