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

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

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

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

Concentration More 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

Concentration Units of Concentration:

Molar Concentration Molarity Unit mainly used in chemistry Molarity is the number of moles of the substance contained in 1L of solution

Molarity mol M L

Molarity mol M L

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

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

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

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

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

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

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

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

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

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

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

Experiment Procedure Example 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

Experiment Procedure Example 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

Experiment Procedure Example 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

Experimental Procedure Example 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

Experimental Procedure Example 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

Experimental Procedure Example 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

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

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

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

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

Dilutions of Solution Concentration and Volume are inversely related

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

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

Dilutions of Solutions Volume Concentration C x V

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

FIND BEAKER

Concentration

Dilution Formula I = Initial F = Final V = Volume C = Concentration

Dilution Formula

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

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].

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

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

Diluting Stock Solutions Stock solutions – are concentrated solutions from the suppliers

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

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?

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

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

DONE WITH THE MOLE

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