1. Chapter 4 Aqueous Reactions and Solutions

2. Solvent Making solutions What the solute and the solvent are Solute dissolved substance doing the dissolving

3. Making solutions Whether a substance will dissolve. How much will dissolve. A substance dissolves faster if- –It is stirred or shaken. –The particles are made smaller. –The temperature is increased.

4. How Much? Solubility- The maximum amount of substance that will dissolve at that temperature (usually g/L). Saturated solution- Contains the maximum amount of dissolved solute Unsaturated solution- Can dissolve more solute Supersaturated- A solution that is temporarily holding more solute than normal, a seed crystal will make it come out

5. Concentration A measure of the amount of solute dissolved in a certain amount of solvent. Concentrated solution has a large amount of solute to solvent. Dilute solution has a small amount of solute to solvent Aqueous chemical reactions don’t happen in grams

6. A. Solution Composition 1. Molarity The number of moles of solute in 1 Liter of the solution. M = moles solute Liter solution

7. Making solutions Pour in a small amount of solvent Then add the solute and dissolve it Then fill to final volume. M x L = moles

8. Example #1 When 23.4g of Na 2 SO 4 is dissolved in water to form 125mL of solution, what is the Molarity? 23.4 g Na 2 SO 4 1 mol = 0.165 mol Na 2 SO 4 142.1 g 0.165 mol = 1.32 M Na 2 SO 4 0.125 L

9. Example #2 How many grams of Na 2 SO 4 is dissolved in water to make 0.350 L of 0.500 M solution? 0.500 M = 0.500 0.500 mol0.350 L = 0.175 mol Na 2 SO 4 L mol L 0.175 mol Na 2 SO 4 142.1 g = 24.9g Na 2 SO 4 mol

10. 2. Dilution Adding water to a solution

11. Dilution The number of moles of solute doesn’t change if you add more solvent. The moles before = the moles after M 1 x V 1 = M 2 x V 2 M 1 and V 1 are the starting concentration and volume. M 2 and V 2 are the ending concentration and volume. Stock solutions are pre-made to known M

12. Practice 2.0 L of a 0.88 M solution are diluted to 3.8 L. What is the new molarity? Need 450 mL of 0.15 M NaOH. All you have available is a 3.0 M stock solution of NaOH. How do you make the required solution? –0.463 M diluted solution –22.5 mL of NaOH and enough water to dilute to final volume of 450 mL total solution

13. B. Properties of Solutions 1. Electrolytes –Ionic compounds dissolve in water –This is called dissociation or ionization –Solutes that produce ions in solution are called electrolytes because their solutions can conduct electricity

14. An ionic compounds dissociates as it dissolves in water Ions separate from the solid and become hydrated or surrounded by water molecules. The ions move freely and the solution is able to conduct electricity. Ionic compounds that dissolve completely are strong electrolytes

15. Strong Electrolytes – 100% Ionization HCl (aq)  H + (aq) + Cl - (aq) 100% ionization Some ionic compounds have low solubilities in water but are still strong electrolytes because what does dissolve is 100% dissociated. Weak Electrolytes – only partially ionize HC 2 H 3 O 2 (aq) H + (aq) + C 2 H 3 O 2 - (aq) NH 3(aq) + H 2 O (l) NH 4 + (aq) + OH - (aq) equilibrium arrow acetic acid ammonia 2 % Ionization hydrochloric acid

16. 2.Most solutions of molecular compounds do not conduct electricity and are called nonelectrolytes The molecules of a nonelectrolyte separate but stay intact. The solution is nonconducting because no ions are generated.

17. Molar Concentration 1.0 M 1.0 M 1.0 M NaCl  Na + + Cl - 1.0 M 2.0 M 1.0 M Na 2 SO 4  2 Na + + SO 4 -2

18. Percent solutions Percent means per 100 so Percent by volume = Volume of solute x 100% Volume of solution indicated %(v/v) What is the percent solution if 25 mL of CH 3 OH is diluted to 150 mL with water?

19. Percent solutions Percent by mass = Mass of solute(g) x 100% Volume of solution(mL) Indicated %(m/v) More common 4.8 g of NaCl are dissolved in 82 mL of solution. What is the percent of the solution? How many grams of salt are there in 52 mL of a 6.3 % solution?