Unit V: The Mole Concept

1. Unit V: The Mole Concept V.6. Molar Concentrations

2. Solution • A Homogeneous mixture • A mixture that looks like a pure substance. • Particles of all substances are completely mixed together

3. Solutions: Homogenous Mixtures • A solute is the substance to be dissolved (*component present in smaller amounts) • The solvent is the one doing the dissolving (*component present in larger amounts) • Universal solvent- generally thought of as water

4. Concentration • The CONCENTRATION of a substance in solution is the amount of the substance which exists in a given volume of solution • In Simple Terms

5. ConcentrationMore Terms • Concentrated solution – there is a large amount of substance dissolved in the solution • A Dilute solution – there is very little substance dissolved in the solution

6. Concentration • Units of Concentration:

7. Molar ConcentrationMolarity • Unit mainly used in chemistry • Molarity is the number of moles of the substance contained in 1L of solution

8. mol M L Molarity

9. mol M L Molarity

10. mol M L Molarity • If we can calculate moles then we can determine grams using our Mole Diagram grams

11. CHEM LINGO • [ Square Brackets ] = Molarity or Molar Concentration • [NaOH]

12. Example 1 • Austin dissolves 40.0 g of NaOH in enough water to make a 200.0 mL solution. What is the molar concentration of NaOH? • [NaOH] = ? M • Plan grams  moles  Molarity

13. Example 1 • Austin dissolves 40.0 g of NaOH in enough water to make a 200.0 mL solution. What is the molar concentration of NaOH? • [NaOH] = ? M • Plan grams  moles  Molarity

14. Example 2 • Angela wants to make a 600.0 mL of 0.60 M CaCl2. What mass of solid CaCl2 should she start with? • Plan: M x L  mol g

15. Example 2 • Angela wants to make a 600.0 mL of 0.60 M CaCl2. What mass of solid CaCl2 should she start with? • Plan: M x L  mol g

16. Example 3 • Chris wants to evaporate some 3.0M NaCl to obtain 26.325 g of NaCl. What volume of solution should she evaporate? • g  mol  L

17. Example 3 • Chris wants to evaporate some 3.0M NaCl to obtain 26.325 g of NaCl. What volume of solution should he evaporate? • g  mol  L

18. Example 4 • Elyse has 4.0 g of NaOH and she wants to make a 0.80 M solution. She should add water to a total volume of what? • Plan: g  mol  L

19. Example 4 • Elyse has 4.0 g of NaOH and she wants to make a 0.80 M solution. She should add water to a total volume of what? • Plan: g  mol  L

20. Experimental Procedure • Give directions in a step wise manner • Rough outline of experimental procedure • Typically want you to figure out the mass or volume required to make a certain solution

21. Experiment ProcedureExample 1 • Blair needs to make 300.0 mL of 0.25 M NaOH. Describe the procedure Blair needs to follow in order to make this solution. • Plan: M x L  mol  g

22. Experiment ProcedureExample 1 • Blair needs to make 300.0 mL of 0.25 M NaOH. Describe the procedure Blair needs to follow in order to make this solution. • Plan: M x L  mol  g

23. Experiment ProcedureExample 1 • Blair needs to make 300.0 mL of 0.25 M NaOH. Describe the procedure Blair needs to follow in order to make this solution. • Plan: M x L  mol  g

24. Experimental ProcedureExample 2 • Mark is asked to give directions to make 250.0 mL of 0.55M K2SO4. What should he say? • M x L  mol  g

25. Experimental ProcedureExample 2 • Mark is asked to give directions to make 250.0 mL of 0.55M K2SO4. What should he say? • M x L  mol  g

26. Experimental ProcedureExample 2 • Mark is asked to give directions to make 250.0 mL of 0.55M K2SO4. What should he say? • M x L  mol  g

27. Experimental ProcedureExample 3 • Tianna needs to tell Savannah how to make a 2.00L solution of 6.0 M NaOH. • Plan: M x L  mol  g

28. Experimental ProcedureExample 3 • Tianna needs to tell Savannah how to make a 2.00L solution of 6.0 M NaOH. • Plan: M x L  mol  g

29. Experimental ProcedureExample 3 • Tianna needs to tell Savannah how to make a 2.00L solution of 6.0 M NaOH. • Plan: M x L  mol  g

30. Hebden • Do Exercises 59(b, d, e & f), 60 (c & e), 62 and 64 on pages 98 of Hebden

31. Dilutions of Solution • Concentration and Volume are inversely related

32. Dilutions of Solution • When we add water the volume increases • Volume ↑ Concentration ↓ • When we remove water the volume decreases • Volume ↓ Concentration ↑

33. Dilutions of Solutions • For the same solution • If we double the volume  the concentration is halved (x ½) • If we triple the volume  the concentration x 1/3

34. Dilutions of Solutions

35. Concentration 50.0 mL of 6.0 M HCl 100.00 mL of 0.30 M HCl Add 50.0 mL of water

36. FIND BEAKER

37. Concentration

38. Dilution Formula • I = Initial • F = Final • V = Volume • C = Concentration

39. Dilution Formula

40. Example • Matt adds 150.0 mL of water to 50.0 mL of 0.60 M solution of HCl. Find the final [HCl] .

41. Example 2 • Connor adds water to 100.0 mL of 0.25 M HF to a volume of 400.0 mL Find the final [HF].

42. Example 3* • Tanner dilutes 60.0 mL of 0.40 M HNO3 to 0.15 M. What is the final volume?

43. Example 3* • Tanner dilutes 60.0 mL of 0.40 M HNO3 to 0.15 M. How much water did Tanner add?

44. Diluting Stock Solutions • Stock solutions – are concentrated solutions from the suppliers

45. 12 M HCl 15 M HNO3 18 M H2SO4 Diluting Stock Solutions

46. Example 4 • Natasha wants to make 100.0 mL of 0.20 M HCl. What volume of 12.0 M HCl should she start with?

47. Example 4 • Natasha is unfamiliar with the ways of chemistry. Explain how she should proceed to make her solution from the concentrated stock solution.

48. Hebden • Do Exercises 78, 82, 89, 91 on pages 102-103 of Hebden • Do Hand-In Assignment #10

49. DONE WITH THE MOLE

50. Unit Test • % mass and % composition • Mass of element when given a mass of a compound • Empirical and Molecular Formulas • Concentration: Solution, Solvent, Solute • Molar concentration/ Molarity • Dilutions of Solutions