 # Spring Semester, 2013 Mrs. L. Fox. Concentration The amount of a dissolved substance occupying a given volume of the solution.

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Spring Semester, 2013 Mrs. L. Fox

Concentration The amount of a dissolved substance occupying a given volume of the solution

Dilute Solutions Contain few solute molecules

Concentrated Solutions Contain many solute molecules

Molarity The number of moles of solute dissolved in 1 liter of solution Symbol is M Units are mol/L A solution that is 0.75 M KCl Contains 0.75 mols of KCl in every liter

Make 1 liter of a 0.75 M solution of KCl Calculate the molar mass of KCl 1 mol K = 39.10 g/mol 1 mol Cl = 35.45 g/mol 1 mol KCl = 39.10 + 35.45 = 74.55 gKCl/mol

Convert the molarity to the sample mass required 0.75 M KCl = 0.75 molsKCl/L * 74.55 g/mol = 55.91 gKCl/L You need to add 55.91 g of KCl to 1 liter of water to make 0.75 M KCl solution

What if you want a smaller amount? To make 150 mL 55.91 g/L * 1 L/1000 mL * 150 mL = 8.39 gKCl

Molarity Calculations M = # mol solute/# L solution

What is the molarity of an aqueous solution containing 40.0 g of glucose (C 6 H 12 O 6 ) in 1.5 L of solution?

What is the molarity of a bleach solution containing 9.5 g of NaOCl per liter of bleach?

Calculate the molarity of 1.60 L of a solution containing 1.55 g of dissolved KBr.

Diluting Stock Solutions Sometimes, the molarity of a solution is not what you want You have to dilute the solution to get the molarity you do want For that, you use M 1 V 1 = M 2 V 2 (In Chem Reference Sheet)

What volume would you use to make 0.50 L of 0.300 M CaCl 2 solution?

21) What volume of a 3.00 M KI solution would make 0.300 L of a 1.25 M solution?

How many mL of 5.0M solution to prepare 100.0mL of 0.25 M H 2 SO 4 ?

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