Concentration of a Solution

1
Concentration of a Solution

• The concentration of a solution is a measure of
  the amount of solute in a given amount of solvent
  or solution.
• Chemists commonly use several different ways to
  quantitatively express the concentration of a
  solution. These include
• Percent Composition by mass
• Parts per million / Part per billion
• Molarity (M)
• Molality (m)

2
Percent Composition by Mass

• Sometimes the amount of solute present in the
  solution is expressed as a percent by mass.
• grams of solute
• Composition -------------------------
  x 100
• grams of solution
• Remember solution is the solute and solvent
  together

3
Percent Composition Sample Problems

• What is the percent composition of a solution
  that contains 115 g NaCl dissolved in 500 g of
  H2O?
• How many grams of KMnO4 are needed to make 500 g
  of a 12.0 KMnO4 solution?

4
Parts per Million (ppm) andParts per Billion
(ppb)
Parts per Million (ppm)

• ppm

? 106
Parts per Billion (ppb)
? 109
ppb
5
What Do You Think?

• A 900.0 g sample of sea water is found to contain
  6.7 x 10 -3 g Zn. Express this concentration in
  ppm.

6
Molarity (M)

• Molarity (M) is the number of moles of solute per
  liter of solution.
• moles of solute (mol)
• Molarity (M) --------------------------------
  
• liters of
  solution (L)

7
Molarity Sample Problems

• What is the molarity of a 0.500 L sample of
  solution that contains 60.0 g of sodium hydroxide
  (NaOH)?
• How many grams of sodium chloride (NaCl) are
  required to prepare 250.0 mL of a 3.00 M solution?

8
Molality (m)

• Molality is the concentration of a solution
  expressed in moles of solute per kilogram of
  solvent.
• moles of solute (mol)
• Molality (m) --------------------------------
  ---
• kilogram of solvent (kg)

9
Molality Sample Problem

• A solution was prepared by dissolving 17.1 g of
  glucose, C6H12O6, in 275 g of water. What is the
  molality (m) of this solution?

10
Wrapping It Up

• Reflect on what you have learned concerning the
  todays topic.
• Respond to the following
• What is the most important thing you learned
  today?
• What is one question you would still like
  answered?
• What is a way what you have learned today
  connects with what you knew before?