Fundamental Chemistry and Hydraulics - Mathematics and Statistics for the Environment - page 356

■ EXAMPLE 14.8
Problem: Find the molarity of 0.03 moles of NaOH in 90 mL of solution.

Solution:

003
0 090

.

.= M 033

.

■ EXAMPLE 14.9
Problem: Find the normality of 0.3 moles CaCl 2 in 300 mL of solution.
Solution :

203
0 300

× .

= 20 . N

.

■ EXAMPLE 14.10
Problem: Find the molality of 5.0 g of NaOH in 500 g of water.

Solution:

50 .

= 02 . m

50 × 0 500 .

14.1.2.8 Simple Solutions and Dilutions
A simple dilution is one in which a unit volume of a liquid material of interest is combined with an
appropriate volume of a solvent liquid to achieve the desired concentration. The dilution factor is the
total number of unit volumes in which a material will be dissolved. The diluted material must then
be thoroughly mixed to achieve the true dilution. For example, a 1:5 dilution entails combining 1
unit volume of diluent (the material to be diluted) plus 4 unit volumes of the solvent medium; 1 + 4
= 5 is the dilution factor. The fact that the number of moles or equivalents of solute does not change
during dilution enables us to calculate the new concentration.

14.1.2.8.1 Simple Dilut ions
We demonstrate the simple dilution or dilution factor method in the following. Suppose we have
a can of orange juice concentrate that is usually diluted with 4 additional cans of cold water (the
dilution solvent), giving a dilution factor of 5; that is, the orange juice concentrate represents 1 unit
volume to which we have added 4 more cans (same unit volumes) of water. So, the orange juice
concentrate is now distributed through 5 unit volumes. This would be called a 1:5 dilution, and the
orange juice is now 1/5 as concentrated at it was originally. So, in a simple dilution, add one less unit
volume of solvent than the desired dilution factor value.

14.1.2.8.2 Serial Dilutions
A serial dilution is simply a series of simple dilutions amplifying the dilution factor quickly, begin-
ning with a small initial quantity of material (e.g., bacterial culture, a chemical, orange juice). The
source of dilution material for each step comes from the diluted material of the previous. In a serial
dilution, the total dilution factor at any point is the product of the individual dilution factor in each
step up to it:

Final dilution factor (DF) = (DF 1 )(DF 2 )(DF 3 ) … (14.8)