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Unit V: The Mole Concept

This guide covers the concept of molar concentrations and homogeneous mixtures in chemistry. It defines key terms such as solute, solvent, concentrated, and dilute solutions. You’ll learn how to calculate molarity, perform dilution calculations, and follow experimental procedures for creating solutions. Examples demonstrate practical applications, including making specified volumes and concentrations from solid substances. Get familiar with the dilution formula and the relationship between volume and concentration for effective solution management.

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Unit V: The Mole Concept

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  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

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