1. Making Solutions and Dilutions Unit 11 – PPT 2

2. What is a solution?  A homogeneous mixture!  Made up of a solute and solvent.  Solvent – Does the dissolving. Usually present in the larger amount.  Solute – Is dissolved. Usually present in the smaller amount.

3. Aqueous Solutions  Water is a good solvent because the molecules are polar.  The oxygen atoms have a partial negative charge.  The hydrogen atoms have a partial positive charge.

4. Hydration  The process of breaking the ions of salts apart.  Ions have charges and attract the opposite charges on the water molecules.

5. Hydration H H O H H O H H O H H O H H O H H O H H O H H O H H O

6. Molarity – Page 13  Measure of the “strength” of a solution  “Strong” has higher molarity  “Weak” has lower molarity  Solution has 2 parts  Solute – what gets mixed in  Solvent – what does the dissolving (typically water) # of moles of solute  Molarity = -------------------------- Liters of solution  Units are moles / Liter or M or M

7. Molarity – Page 13  There is a distinction between mole and molar  Moles represent a quantity  Molarity represents a concentration  So 0.1M is a concentration of.1 moles / 1 liter of solution, it does not mean.1 moles.

8. Making Solutions – Page 14  Example: Make a 1M solution using KBr 1 mole of KBr ------------------- 1 Liter or 1000 ml H 2 O  What units do we “weigh” in?  Grams  How do we convert moles to grams??  Moles x Molar Mass

9. Page 15, Problem #1  Determine the grams of solute needed to make 1.00L of a 1.0M solution of NaCl.

10. Page 15, Problem 2  Determine the grams of solute needed to make 1.00L of a 0.50M solution of sodium nitrate.

11. Dilutions – Page 17  Use a concentrated stock (standard) solution to make a more dilute solution.  Start with a small amount of the standard solution and add water to lower the concentration.  Since moles of solute are constant, can set up a proportion.  M 1 V 1 = M 2 V 2

12. Page 17, Problem #2  What volume of 0.250M KCl is needed to make 100.0mL of 0.100M KCl solution?

13. Page 17, Problem #3  Concentrated sulfuric acid is 18.0M. What volume of this standard solution is needed to make 2.00L of 1.00M sulfuric acid?