Transcript Solution and Concentration

Solutions
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SEPARATING SOLUTIONS
CONCENTRATIONS AND MOLARITY
SOLUBILITY AND DISSOLVING
Concentration
 Concentration – the amount of particular substance
in a given quantity of a solution.
 Concentration can be expressed in many forms:
 ppm – parts per million
 molarity – moles solute over liters solution
 molality – moles solute over kg of solvent
 We can make these calculations if we know the
quantity of solute and volume (quantity) of solvent.
Molarity
 We often use molarity when dealing with
concentrations.
 Molarity – a concentrations unit of a solution
expressed as moles of solute dissolved per liter of
solution.
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How MUCH solute is in how MUCH solvent
M = mol / L
Molarity
 Molarity describes a solution in terms of volume of
solution not volume of solvent.
 If you need 1 Liter of solution, you are NOT adding 1
Liter of solvent. You must add “enough” solvent to
make the total volume 1 Liter.
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The solute will take up some of the volume.
 You can determine the number of moles of solute if
you know the mass used.
Practice Problems
 What is the molarity of a potassium chloride solution
that has a volume of 400.0 mL and contains 85.0 g
KCl?
Practice on your own
 Vinegar contains 5.0 g acetic acid, CH3COOH, in
100.0 mL of solution. Calculate the molarity of the
acetic acid in the vinegar.
 What mass of KCl is present in 25 mL of a 0.85 M
solution of potassium chloride?
Solution Stoichiometry
 Solutions of known concentrations are often used in
the lab.
 When reactions involving these solutions occur, we
can use stoichiometry to calculate the mass of
products we should obtain.
 We could then use this amount of product formed
along with the total volume of the system to
determine the concentration of product formed.
Soln. Stoich. Practice
 An excess of zinc is added to 125 mL of 0.100 M HCl
solution. What mass of zinc chloride is formed?
___ Zn + ___ HCl  ___ ZnCl2 + ___H2
Soln. Stoich. Practice
 What volume (in milliliters) of a 0.500 M solution of
copper (II) sulfate is needed to react with an excess
of aluminum to provide 11.0 grams of copper?
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Hint: Step 1: Write out and balance your reaction
 Work on Solution Stoich WKST – Due tomorrow
 Vocab Sheet due
Tuesday