1. Chapter 14 Ions in Aqueous Solutions & Colligative Properties

2. Sect. 14-1: Compounds in Aqueous Solutions Dissociation – separation of ions that occurs when an ionic compound dissolves in water  Different compounds produce different number of ions in solution  NaCl  Na + + Cl - 1 mol 1 mol 1 mol  CaCl 2  Ca 2+ + 2Cl - 1 mol 1 mol 2 mol

3. Solubility rules – pg. 427  Helps to determine what is soluble/insoluble in water  Helps predict state of products of a double replacement reaction

4. Ionic equation – separates all aqueous compounds into their ions Net ionic equation – shows the compounds and ions that undergo a chemical change during the reaction in aqueous solution Spectator ion – ions that do not take part in the chemical reaction and are present on both sides of the equation

5. Ionization – ions are formed from solute molecules (typically polar compounds) Hydronium ion – H 3 O + ion; formed by hydrogen ion combining with water Strong electrolyte – a compound in which almost all of the dissolved compound exists as ions in aqueous solution Weak electrolyte – compound in which a relatively small amount of the dissolved compound exists as ions in solution

6. Sect. 14-2: Colligative Properties of Solutions Colligative properties – properties that depend on the concentration of solute particles, but not on their identity  Vapor-pressure lowering  Freezing-point depression  Boiling-point elevation  Osmotic pressure

7. http://img.sparknotes.com/figures/A/a355d48810a7fa33761d1f32c3099d7b/fpdep.gif

8. Non-volatile substance – a substance that has little tendency to become a gas under existing conditions Vapor-pressure lowering occurs because the presence of the solute lowers the amount of liquid present at the surface, which means a smaller amount of it can become a gas http://images.google.com/imgres?imgurl=http://faculty.virginia.edu/lehmannlab/images/badchem/Solutionweb.gif&imgrefurl=http://faculty.virginia.edu/lehmannlab/badchemistry.html&h=483&w= 650&sz=38&hl=en&start=6&tbnid=OTmcVTKDNVCjvM:&tbnh=102&tbnw=137&prev=/images%3Fq%3Dvapor-%2Bpressure%2Blowering%26gbv%3D2%26hl%3Den%26safe%3Dactive

9. Molal freezing-point constant (K f ) – the freezing-point depression of the solvent in a 1m solution of a non-volatile, non-electrolyte solute  Specific for each solvent  Found on pg. 438 Freezing-point depression (Δt f ) - difference in freezing points between the pure solvent and the solution  Δt f = K f m

10. Example: What is the freezing-point depression of water in a solution of 17.1g of sucrose (C12H22O11) and 200 g of water? What is the actual freezing point of the solution?

11. Molal boiling-point constant (K b ) – the boiling- point elevation of the solvent in a 1m solution of a non-volatile, non-electrolyte solute  Specific to each solvent  Found on pg. 438 Boiling-point elevation (Δt b ) - difference in boiling points between the pure solvent and the solution  Δt b = K b m

12. Example: What is the boiling-point elevation of a solution made from 20.0g of a non- electrolyte solute and 400.0g of water? The molar mass of the solute is 62.0g.

13. Osmotic pressure Semipermeable membranes – allow the movement of some particles and blocks others Osmosis – movement of solvent through a semipermeable membrane from higher to lower concentration Osmotic pressure – external pressure that must be applied to stop osmosis http://images.google.com/imgres?imgurl=http://cache.eb.com/eb/image%3Fid%3D54956%26rendTypeId%3D4&imgrefurl=http://www.britannica.com/ebc/art-66778/Diffusion-of-water-across-a- semipermeable-membrane-Water-diffuses- down&h=256&w=348&sz=29&hl=en&start=2&tbnid=JQRVGtARuvAb_M:&tbnh=88&tbnw=120&prev=/images%3Fq%3Dsemipermeable%2Bmembrane%26gbv%3D2%26hl%3Den%26safe%3Dactive

14. Electrolytes and Colligative Properties Electrolytes dissolve to produce more than one mole of solute particles for each mole of the compound that was dissolved, therefore they have more of an effect on colligative properties than non-electrolytes When doing colligative property calculations with electrolytes, you must multiply the actual molality times the number of ions it produces in solution

15. Example: What is the expected change in the freezing point of water in a solution of 62.5g of barium nitrate Ba(NO 3 ) 2 in 1.00kg of water?