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Wednesday February 29, 2012

Wednesday February 29, 2012. ( Discussion – Molarity: Concentration of Solutions; WS – Molarity). Bell Ringer Wednesday, 2-29-12. In order for a solution to conduct electrical current, the solute particles must display what two properties?. T he solute particles must be charged.

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Wednesday February 29, 2012

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  1. WednesdayFebruary 29, 2012 (Discussion – Molarity: Concentration of Solutions; WS – Molarity)

  2. Bell RingerWednesday, 2-29-12 In order for a solution to conduct electrical current, the solute particles must display what two properties? The solute particles must be charged. The solute particles must be free to move about.

  3. Announcements • I will be available this afternoon until 4:45.

  4. Begin Worksheet • Molarity

  5. Concentration of Solutions • The concentration of a solution is a measure of the amount of solute in a given amount of solvent or solution. • Some medications are solutions of drugs - a one-teaspoon dose at the correct concentration might cure the patient, while the same dose in the wrong concentration might kill the patient. • The way of expressing the concentrations of solutions is molarity

  6. Concentration of Solutions • Sometimes solutions are referred to as dilute or concentrated. • Dilute just means that there is a relatively small amount of solute in a solvent. • Concentrated means that there is a relatively large amount of solute in a solvent. • Note that these terms are unrelated to the degree to which a solution is saturated – a saturated solution of a substance that is not very soluble might be very dilute.

  7. Molarity • Molarity is the number of moles of solute in one liter of solution. • The symbol for molarity is M. • To find the molarity of a solution, you must know the molar mass of the solute.

  8. Molarity • Ex) a “one-molar” solution of sodium hydroxide, NaOH, contains one mole of NaOH in every liter of solution. • The concentration of a one-molar solution of sodium hydroxide is written as 1 M NaOH. • One mole of NaOH has a mass of 40.0 g - if this quantity of NaOH is dissolved in enough water to make exactly 1.00 L of solution, the solution is a 1 M solution. • If 20.0 g of NaOH, which is 0.500 mol, is dissolved in enough water to make 1.00 L of solution, a 0.500 M NaOH solution is produced.

  9. Molarity • This relationship between molarity, moles, and volume may be expressed in the following way:

  10. Molarity • If twice the molar mass of NaOH, 80.0 g, is dissolved in enough water to make 1 L of solution, a 2M solution is produced. • The molarity of any solution can be calculated by dividing the number of moles of solute by the number of liters of solution. • Note that a 1 M solution is not made by adding 1 mol of solute to 1 L of solvent.

  11. Molarity • In such a case, the final total volume of the solution would not be 1 L. • Instead, 1 mol of solute is first dissolved in less than 1 L of solvent, then the resulting solution is carefully diluted with more solvent to bring the total volume to 1 L.

  12. Molarity Sample Problem #1 You have 3.50 L of solution that contains 90.0 g of sodium chloride, NaCl. What is the molarity of that solution? Sample Problem #2 You have 0.8 L of a 0.5 M HCl solution. How many moles of HCl does this solution contain?

  13. Complete Worksheet • Molarity

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