1. Revision Lectures: Part 1 – Dissolving Solubility Precipitation Concentration

2. Water as a Solvent - Dissolving 3 types of Dissolving 1. Polar Covalent Compounds that form H-Bonds with water -Must contain a polar group -The hydrogen bonds between the water molecules are broken -The hydrogen bonds between polar molecules are broken -Hydrogen bonds form between water and covalent polar compound

3. 2. Polar Covalent Molecular Compounds that Ionise -Must have Polar Covalent Bonds (e.g. HCl) -When placed in water the electrostatic attraction between water and molecule causes polar bond to break (remember H under attack) -Leaves H + and anion -Covalent bond forms between H + and water making H 3 O+ -Common examples HNO 3, H 2 SO 4

4. 3. Ionic Compounds that Dissociate -Ionic solids exist in 3D lattices -Water molecules attracted to ions that exist in lattice -Water ‘picks off’ ions from the surface, this action continues -When ionic compound dissolves in water, ion is surrounded by water

5. Remember that “Like Dissolves Like” (polar substances dissolve polar compounds) Not all things are soluble...

6. Solubility Solubility – The maximum amount of solute that can be dissolved in a given amount of solvent at a given temperature Can use a solubility curve to demonstrate solubility

7. 1. Each point ON the graph is a SATURATED 2. Each point BELOW graph is UNSATURATED 3. Each point ABOVE graph is SUPERSATURATED 4. Mass of solute PER 100G OF SOLVENT AT X°

8. The solubility of liquids and solids INCREASE as you INCREASE the temperature The solubility of Gases DECREASE as you INCREASE the temperature (think of a kettle boiling, what are the bubbles? The solubility of Gases INCREASES as you INCREASE the pressure (think of carbon dioxide contained in a coke can)

9. Concentration 2 ways of expressing Concentration 1. Mass of Solute per LITRE of Solution (eg. g/L, mg/L etc) Know how to convert from mL – L – KL etc 2.Amount in Mol of solute per LITRE of solution Unit – M (Molar, moles per litre)

10. To Convert between g/L and mol/L Remember : C 1 V 1 = C 2 V 2 ALL volume measurements are in L! Don’t forget Q 35 page 218 Other forms: %(w/w) (g/100g) %(v/v) same units for both (eg L and L) %(w/v) (g/100mL) Mass solute per mass of solution

11. Precipitation When two solutions are mixed together sometimes an insoluble compound forms – a precipitate Remember the ‘Ion swap’ Eg. K 2 S(aq) + MgCl 2 (aq) →MgS(s) + 2KCl(aq) To find out which is your precipitate consult your solubility table! (p 199)

12. Ionic Equations – when ionic substances dissolve in water they dissociate Any ions that appear the same on both sides are deleted (spectator ions) Remember to BALANCE e.g. K 2 S(aq) + MgCl 2 (aq) →MgS(s) + 2KCl(aq) 2K + (aq) + S 2- (aq) + Mg 2+ (aq) + 2Cl - (aq)→ MgS(s) + 2K + (aq) +2Cl - (aq) S 2- (aq) + Mg 2+ (aq) → MgS(s)