1. Review: - ionic, polar, very soluble HCO HHH Na + Cl - ( - ) ( + ) - covalent, polar, very soluble HCO HHH ( - ) ( + ) C HH - covalent, polar, soluble HCO HHH ( - ) ( + ) C HHC HHC HH - covalent, slightly polar, not very soluble

2. Review continued: - covalent, non-polar, not soluble HCH HHC HHC HHC HHC HH HC HHC HHHC HH HC HHH

3. Solubility & Polarity continued Water molecules interact with other water molecules creating “surface tension” HH O ( + ) ( + ) ( - ) HH O ( + ) ( + ) ( - ) “hydrogen bonding”

4. Summary Polar Compounds Non-Polar Compounds Ionic Covalent Covalent NaCl NaOH KBr CaSO 4 H2OH2OH2OH2O Alcohol Sugars Antifreeze Fats Oils Hydrocarbons Plastics “like dissolves like” Polar substances dissolve in other polar substances and non-polar substances dissolve in other non-polar substances

5. Concentration Calculations e.g.: Concentration amount of solute amount of solute volume of solution = 2.00L of an NaCl solution contains 20.5g of NaCl. Express this concentration in moles per litre. 20.5g 2.00L 1 mole 58.5g 58.5g = 0.174 mol/L Square brackets mean molar concentration and M represents mol / L In the previous example: [ NaCl ] = 0.174 M “molar”

6. Practice Calculations 1. Calculate the molar concentrations: a) 1.0L of solution contains 0.26 mol of HCl b) 4.0L of solution contains 2.8 mol HNO 3 c) 250mL of solution contains 25.0g NaCl d) 50.0mL of solution contains 0.070mol NH 4 Cl e) 600.0mL of solution contains 1.50g of CaCO 3 f) 325mL of solution contains 10.0g of (NH 4 ) 2 CO 3 2. How many moles of NaCl are contained in 3.0L of a 0.20M solution of NaCl? 3. What mass of CaCl 2 is contained in 2.5L of a solution of 1.0M CaCl 2 ? 4. What mass of NaOH would be needed to make 2.0L of a 0.28M solution of NaOH?