Many calculations in chemistry require that we convert quantities
from one set of units to another. Whether we are trying to convert between the
British system of units and the SI system of units, or within the SI system
of units, we can do this by using conversion factors.
For examples,
If we wish to convert between meter and inch, we would need the conversion
factor 1 meter = 39 inches.
If we wish to convert between kilogram and pound, we would need the conversion
factor 1 kilogram = 2.2 pounds.
If we wish to convert between liter and milliliter, we would need the conversion
factor 1 liter = 1000 milliliter.
The approach to problem solving via inspecting the units
of measurments is called dimensional analysis. The basic setup is ummarized
in the following steps:
Identify the unit in the given quantity of measurement. This is your
information given.
Identify the unit that you need to present the answer. This is your
information sought.
Figure out the conversion factor to convert
the unit from I to II and write the conversion factor as a fraction.
Set up the problem as shown below to ensure that units cancel in such a
way that you are left with the unit in II.
(information given) x (conversion factor(s)) = information
sought
Do you know how to express 0.5 mg inµg?
Click on the button if you are unsure.
Section
2.8 Dimensional
Analysis
Method of
Problem Solving
for
Conversions ..p33
Section
2.8
