36.4 KJ A ? g A ? kJ A

------------ * -------- = --------------

g A mol A mol A

Fill up the missing details. Notice how the units cancel?

To cancel the unit g A in the first term, you need to have g A

in the numerator of your conversion factor.

The conversion factor is the relative mass per mole of A.

It can be stated as either:

72 g A 1 mol A

------ or -------

mol A 72 g A

Since 72 g A = 1 mol A, the two ratios are virtually equal to 1.

Thus, it does not change the value of the original term that it

is multiplied to, but it only changes the units. This is called

*dimensional analysis.*

To give you another example.

To convert say 1250 inches to miles:

Is there a direct conversion from inches to miles that you know of?

If none, then how about feet to mile? There is! It is 5,280 feet per mile.

Now you work your way by converting inches to ____ first then ____ to miles. Here it is:

? feet 1 ?

1250 inches * ---------- * --------- = 0.0197 or 1.97 x 10^-2 mile

? inches ? feet

Practice and more practice. What is important is if you want to cancel the units in the denominator, then you should multiply by a conversion factor with the same unit in the numerator.

God bless.