SOLUTIONS
Substances that dissolve readily in water have ionic or polar covalent bonding. They fall into 3 groups:
•Polar covalent compounds that form hydrogen bonds with water.
•Polar covalent molecular compounds that ionise.
•Ionic compounds.
Polar covalent compounds that form hydrogen bonds with water:
•For Example – Ethanol in water.
H20
•C2H5OH (l) → C2H5OH (aq)
•Hydrogen bonding between ethanol molecule and water molecules.
Polar covalent molecular compounds that ionise :
•For Example – HCl molecules in water.
•HCl (l) + H20 (l) → H30+ (aq) + Cl- (aq)
•Molecules react forming ions.
•Ion-dipole attractions between ions formed and polar water molecules.
Ionic lattice compounds:
•For Example – NaCl and water.
H20
•NaCl (s) → Na+ (aq) + Cl– (aq)
•Ionic compound dissolves in water separating into its ions.
•Ion-dipole attractions between ions formed and polar water molecules.
Substances that dissolve readily in water have ionic or polar covalent bonding. They fall into 3 groups:
•Polar covalent compounds that form hydrogen bonds with water.
•Polar covalent molecular compounds that ionise.
•Ionic compounds.
Polar covalent compounds that form hydrogen bonds with water:
•For Example – Ethanol in water.
H20
•C2H5OH (l) → C2H5OH (aq)
•Hydrogen bonding between ethanol molecule and water molecules.
Polar covalent molecular compounds that ionise :
•For Example – HCl molecules in water.
•HCl (l) + H20 (l) → H30+ (aq) + Cl- (aq)
•Molecules react forming ions.
•Ion-dipole attractions between ions formed and polar water molecules.
Ionic lattice compounds:
•For Example – NaCl and water.
H20
•NaCl (s) → Na+ (aq) + Cl– (aq)
•Ionic compound dissolves in water separating into its ions.
•Ion-dipole attractions between ions formed and polar water molecules.
SOLUBILITY OF SOLIDS IN WATER
•Not all ionic compounds dissolve readily in water.
•For Example – Limestone (CaCO3) is almost insoluble in water.
•Solubility of ionic compounds varies with temperature.
Solubility curve diagram courtesy of By TheKiteGuy - Template:Https://commons.wikimedia.org/wiki/File:SolubilityVsTemperature.png, CC0, https://commons.wikimedia.org/w/index.php?curid=51036796
The SNAPE rule
•This rule states that salts that contain one or more of the following ions are soluble:
•Sodium (Na+)
•Nitrate (NO3-)
•Ammonium (NH4+)
•Potassium (K+)
•Ethanoate (CH3COO-)
•This rule states that salts that contain one or more of the following ions are soluble:
•Sodium (Na+)
•Nitrate (NO3-)
•Ammonium (NH4+)
•Potassium (K+)
•Ethanoate (CH3COO-)
PREDICTING SOLUBILITY
•Is barium sulfide soluble?
•Check table for Ba2+ and S2-.
•Barium is not present in the table but most sulfides are insoluble. Barium is not in the exceptions column.
•Answer- Barium sulfide is insoluble.
•Is barium sulfide soluble?
•Check table for Ba2+ and S2-.
•Barium is not present in the table but most sulfides are insoluble. Barium is not in the exceptions column.
•Answer- Barium sulfide is insoluble.