Transcript Concentration of Solutions

Concentration of
Solutions
Concentrations of Solutions
(Section 2.5)
Concentration = quantity of solute
quantity of solution
A solution is dilute if there is a relatively small amount
of solute per unit volume of solution.
A solution is concentrated if there is a relatively large
amount of solute per unit volume of solution.
Percentage Concentration
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A photographic “stop bath” contains 160 mL of
acetic acid in 600 mL of solution. What is the (v/v)
percentage concentration of acetic acid in the stop
bath?
A salt solution is formed by mixing 2.80 g of NaCl in
enough water to make exactly 250 mL of solution.
What is the (w/v) percentage concentration of salt in
this solution?
Concentrations of very small amounts
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ppm (parts per million)
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ppb (parts per billion)
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ppt (parts per trillion)
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ppm = milligrams (mg)
volume in Litres
The maximum permitted mass of lead in 1.0 L of
public drinking water is 5.0 X 10 -5 g. What is this
concentration in ppm?
Molar Concentration
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Molar concentration is sometimes indicated
by square brackets [ ]
i.e [NH3] means the molar concentration of NH3
[1.5] means a concentration of 1.5 mol/L
A solution is prepared by dissolving 1.68 g of CuSO4
in enough water to make 150 mL of solution.
Calculate the molar concentration of CuSO4.
Sodium carbonate (Na2CO3) is a water softenerr that
makes up a significant part of laundry detergent. A
student dissolves 5.00 g of sodium carbonate in
enough water to make 250 mL of solution. What is
the molar concentration of Na2CO3 in this case?
A sample of NH3solution has a concentration of 14.8
mol/L. How many moles of NH3 would be present in
a 1.50 L bottle of this solution?
What volume of a 5.0 mol/L glucose solution contains
2.5 mol of glucose?
Diluting Aqueous Solutions
A stock solution is a solution whose concentration
is precisely known.
Dilution is the process of decreasing the
concentration of a solution by adding more
solvent (usually water).
When more solvent is added to a solution it does not change the
amount of solute present. It only changes the volume of the
solution.
If you double the volume of a 6% H2O2 solution what will the new
concentration be?
3% H2O2
There is a fairly simple equation that relates the initial and final
concentration and volumes when a solution is diluted.
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Ci = the initial concentration of the solution
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Cf = the final concentration of the solution
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Vi = the initial volume of the solution
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Vf = the final volume of the solution
CiVi = CfVf
Using this equation you can solve for any of the variables. Just be
careful that if you have two concentrations that they are measured
in the same unit or if you have two volumes that they are both be
measured in the same unit.
Calculate the new concentration (molarity) if enough
water is added to 100mL of 0.25mol/L sodium
chloride to make up 1.5L.
Calculate the volume to which 500mL of 0.02mol/L
coppper sulfate solution must be diluted to make a
new concentration of 0.001mol/L.
If I have 340 mL of a 0.5 M NaBr solution, what will the
concentration be if I add 560 mL more water to it?
If I leave 750 mL of 0.50 M sodium chloride solution uncovered on a
windowsill and 150 mL of the solvent evaporates, what will the new
concentration of the sodium chloride solution be?
To what volume would I need to add water to the evaporated
solution in problem 3 to get a solution with a concentration of
0.25 M?