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Concentration of Solutions
Spring Semester, 2013Mrs. L. Fox
ConcentrationThe amount of a dissolved substance
occupying a given volume of the solution
Dilute SolutionsContain few solute molecules
Concentrated SolutionsContain many solute molecules
MolarityThe number of moles of solute dissolved in 1
liter of solutionSymbol is MUnits are mol/LA 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 KClCalculate the molar mass of KCl
1 mol K = 39.10 g/mol1 mol Cl = 35.45 g/mol1 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 CalculationsM = # mol solute/# L solution
What is the molarity of an aqueous solution containing 40.0 g of glucose (C6H12O6) 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 SolutionsSometimes, the molarity of a solution is not
what you wantYou have to dilute the solution to get the
molarity you do wantFor that, you use
M1V1 = M2V2 (In Chem Reference Sheet)
What volume would you use to make 0.50 L of 0.300 M CaCl2 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 H2SO4?