2. Solutions and Mixtures

3. Aqueous Solutions pg. 292 Something is dissolved in water…the something can vary. When compounds dissolve in water, it means that they break apart into the ions that make them up. The only covalent compounds that do this are acids. Ionic compounds dissolve in water easily. Example of ionic equation

4. What are solutions? Solutions are homogeneous mixtures containing two or more substances called the solute and the solvent. Solute: dissolves (less) Solvent: dissolving medium (more)

5. Solutions Vocabulary Soluble: able to be dissolved in a solvent Insoluble: unable to be dissolved in a solvent Immiscible: two liquids that cannot dissolve or mix (oil and water) Miscible: two liquids that are soluble in each other

6. Solvation When a solution forms, solute particles separate from one another and the solute and solvent particles must mix. The solvent particles completely surround the surface of the solute, pull them apart, and surround the solute particles. Solvation: process of solvent particles surrounding the solute particles forming a solution.

7. “Like dissolves like.” To determine whether a solvent and solute are alike, you must examine the bonding and the polarity of the particles and the intermolecular forces between particles. These properties affect solvation, the process of forming a solution.

8. Factors Affecting Rate of Solvation Solute and solvent particles coming in contact with each other is KEY in forming a solution. Increasing the contact will increase the formation of the solution. 3 ways to increase contact or collisions: 1.Agitating the mixture 2.Increasing the surface area of the solute 3.Increasing the temperature of the solvent

9. Solubility Maximum amount of solute that will dissolve in a solvent at a particular temperature and pressure Saturated: contains max. amount at that T&P Unsaturated: contains less than max. amount at that T&P Supersaturated: contains more than max. amount at that T&P HUH?

10. Temperature and Pressure HIGH temperature: at very high temperatures, more solid solute can dissolve in a liquid solvent. [supersaturated solutions start this way] HIGH pressure: at high pressures, more gaseous solute can dissolve in a liquid solvent. [soft drinks are made this way]

11. Solubility Chart

12. Concentration of Solutions The concentration of a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution. Molarity: most common units of solution concentration; # of moles solute dissolved in one liter of the solution

13. Molarity Calculations Molarity: moles of solute liter of solution If given grams, remember to change it to moles.

14. Stop

15. Practical Stuff: Making a Solution If given a stronger solution, you can dilute it (water it down) to make the weaker solution that you want.

16. Diluting Solutions Beaker #1 contains concentrated salt water, 2M NaCl. I want to dilute it. What do I do? Add more water…in other words, add more solvent. TO DILUTE A SOLUTION, ADD MORE SOLVENT.

17. Diluting Solutions Does adding solvent affect the amount of solute in the solution? NO

18. Diluting Solutions If you already have a solution molarity, but you want a different molarity: USE THIS EQUATION: M 1 V 1 = M 2 V 2

19. Sample Calculation I have 500.0mL of a 2M NaCl solution, but I want a 1M NaCl solution. How much water should I add?

20. Sample Calculations I want 0.50L of a 0.300M CaCl 2 solution, but I have a 2.00M CaCl 2 solution. How much of the 2.00M CaCl 2 solution is needed?

21. Practice Notes: Practice Problems.

22. Molality Another unit for concentration m=moles of solute per kilogram of solvent

23. Colligative Properties Physical properties of solutions that change depending on the number of solute particles in solution Vapor pressure lowering Boiling point elevation Freezing point depression*

24. Freezing Point Depression The temperature of a solution is always lower than the temperature of pure solvent. The freezing point depression is the difference between the freezing point of the solution and that of the solvent. Salt on icy roads Ice Cream

25. Reactions that form Precipitates pg. 292-293 When solutions of sodium hydroxide and copper(II) chloride are mixed, a precipitate forms…copper(II) hydroxide. What does solutions of sodium hydroxide and copper(II) chloride mean? So the ionic compounds fall apart…and the copper and hydroxide ions come together to form the solid copper(II) hydroxide. The sodium and chloride ions remain dissolved.

26. Ionic Equations pg. 293 Ionic equations show all the particles in a solution dissolved as ions. Complete ionic equations show all ions and precipitates. Net ionic equations show only how the precipitate came to form…all spectator ions are removed. Example