March 3, 2008 Objectives: define molarity and practice calculating ...

March 3, 2008
Objectives:
­ define molarity and practice calculating concentrations
Molarity ­ amount of solute dissolved per liter of solvent (mols/L = M)
Solute ­ substance being dissolved (sugar into water)
Solvent ­ dissolving agent (most of the time ­ water)
Types of Problems
1. From Dilution ­ M 1 V 1 = M 2 V 2
Example ­ How much 12.0 M HCl would be needed to make 3.0 L of 0.50
M HCl?
2. From Mass
Example ­ What is the molarity of 34.5 g of silver chloride dissolved in 3.0 L
of water?
1

3. Calculating the number of moles per ion
Example ­ How many moles of each ion are present in 1.25 L of
0.250 M Na 3 PO 4 solution?
4. Stoichiometry of Solution Reactions
Example ­ One way to determine the amount of chloride ion in a water
sample is to titrate the sample with standard AgNO 3 solution to produce
solid AgCl according to this reaction: Ag + (aq) + Cl ­ (aq) AgCl (s)
If a 25.0 mL water sample requires 27.2 mL of 0.104 M AgNO 3 in such a
titration, what is the concentration of Cl ­ in the sample?
2