Solutions and Concentrations
Notes Page 5
SOLUTIONS
A
homogenous
mixture of
two or more
substances
2 PARTS OF A SOLUTION
• SOLUTE
• A solute is the dissolved substance in a solution.
Sugar in soda
Carbon dioxide in soda
Salt in salt water
• SOLVENT
• A solvent is the dissolving medium in a solution.
•
Water in salt water
Water in soda
Molarity = concentration
•Amount of substance (mol)
•Volume of mixture (L)
• Unit = mol/L or M
• 1.0 M = 1 molar
• 12.0 M = 12 molar
solUTE over solVENT
Example 1
• 1.5 mol of NaCl are dissolved in 1 L of water.
What is the molarity of the solution?
• 1.5 mol NaCl = 1.5 mol/L or 1.5 M
• 1 L H2O
Example 2
• 100 g of NaCl are dissolved in 1 L of water.
What is the molarity of the solution?
• 100 g NaCl |1 mol NaCl = 1.71 mol
58.44 g NaCl
• 1.71 mol NaCl =
1L
1.71 M
Example 3
• 100 g of NaCl are dissolved in 250 mL of water.
What is the molarity of the solution?
• 100 g NaCl |1 mol NaCl = 1.71mol
•
58.44 g NaCl
• 250 mL / 103 mL = 0.25 L
• 1.71 mol NaCl =
6.84 M
0.25 L
Example 4
• How many moles of NaCl are in 500 mL of a 0.25 M solution?
• Basic formula: M = mol
L
• Convert: 500 mL = 0.5 L
• 0.25 M = mol
0.5 L
=
0.5 L x 0.25 M = mol
= 0.125 mol NaCl
Example 5
• How many grams of NaCl are in 500 mL of a 2.25 M solution?
• Basic formula: M = mol
L
• Convert: 500 mL = 0.5 L
• 2.25 M = mol
=
0.5 L x 2.25 M = mol
0.5 L
= 1.125 mol NaCl
• 1.125 mol NaCl | 58.44 g NaCl = 65.75 g NaCl
1 mol