2. Concentration of Solutions Ch 14.2-14.3 (RB) / Chapter 16 (BB)

3. Heterogeneous Mixtures A heterogeneous mixture is a mixture that does not have a uniform composition and in which the individual substances remain distinct. Suspensions are mixtures containing particles that settle out if left undisturbed. Suspensions

4. Solutions are homogeneous mixtures that contain two or more substances called the solute and solvent. Most solutions are liquids, but gaseous and solid solutions exist. Homogeneous Mixtures

5. Homogenous Mixtures

6. Solutions solution – a substance dissolved in a liquid. solvent – the liquid, solute – the substance being disolved.

7. Water—The Super Solvent! Water is an universal solvent. Water dissolves more solutes than anything else! A dissolved solid falls apart into its individual constituent particles, either ions or molecules. This explains why they are usually transparent. http://www.youtube.com/watch?v=EBfGcTAJF4o&playnext_from=TL&vi deos=gRLBCOaBXS0 http://www.youtube.com/watch?v=EBfGcTAJF4o&playnext_from=TL&vi deos=gRLBCOaBXS0

8. Factors that affect solubility Like tends to dissolve like. Polar solvent dissolves polar solutes Non-polar solute dissolves in non-polar solvents Molecular Size: Big, heavy molecules tend to be less soluble than small light molecules. It is harder for the solvent to “cage” the solute. Temperature: As temperature rises, agitated molecules or ions break their bonds more easily. So as temperature goes up, so does solubility.

9. Solution Equilibrium The maximum concentration of solute that a solvent can hold at a certain temperature is called saturated solution. If large amounts of solute are added to a solution at high temperature then allowed to slowly cool down, then a super saturated solution may occur.

10. Concentration The concentration of a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution.concentration Concentration can be described as concentrated or dilute.

11. Concentration Concentrated vs. Dilute Concentrated: lots of solute per unit of volume. Dilute: little solute per unit of volume.

13. Concentration Units Dilute and Concentrated can be ambiguous. What is dilute? What is concentrated? Chemists like their numbers!

14. Example Problem p. 149 If 18.0 grams of sodium sulfate are dissolved in 207.0 grams of water, what is the percent concentration of this solution? X 100 = 8.00% = x 100 % by mass = g solute g solution 18.0g solute 225g solution

15. Molarity Molarity is the number of moles of solute dissolved per liter of solution. Molarity

16. Example Problem #1 p. 142 Calculate the molarity of 1500 ml of solution that contains 200.0g MgCl 2. 200.0g MgCl 2 1molMgCl 2 1000 ml 1500ml 95.2g MgCl 2 1 L =1.40mol/L or M

17. Example Problem #2 p. 142 Calculate the molarity of a 500 cm 3 solution that contains 10.0 g of sodium hydroxide. To solve: Convert 10.0 g of NaOH per 500 cm 3 to moles of NaOH per dm 3 of soultion. 10.0g NaOH 1 mol NaOH 1000 cm 3 500 cm 3 40.0 g NaOH 1dm 3 Answer: 0.500 mol/dm 3 = 0.500 M

18. Dilutions If you want a solution of lesser concentration you will need to dilute it! Add more solvent! The total number of moles of solute does not change M 1 x V 1 = M 2 x V 2 M = Molarity & V = Volume M 1 and V 1 = “old” or stock M 2 and V 2 = “new” or dilute

19. Example #1 It is necessary to make a.500M solution of HCl from 250.0 ml of a 2.00M solution of HCl. What is the volume of the new solution? M 1 x V 1 = M 2 x V 2 2.00M x 0.250 L = 0.500M x V 2 V 2 = 1.00 L So… you add enough solvent to bring the new volume up to 1L. How much do you add? 1.00 L – 0.250 L = 0.750 L solve for V 2 = 2.00M x 0.250ml 0.500M

20. THE END Questions??? HW BB Chpt 16: 1 (a-c), 2 (a-c), 10 (a-c), 13 Chpt 18: 1-3 a-c, 10 a-c