Multiply the GMW, expressed in grams per mole, times 1/TPIV, expressed in
moles per equivalent, used as an appropriate factor.
56.1 g
mol
------ X ------ = 56.1 g/Eq
mol
1 Eq
b. Example 2. Find the GEW of CaCO3.2H2O.
Solution. Determine the GMW of the compound.
NOTE:
Water, being a relatively neutral substance, is not considered when
determining the TPIV of a hydrate. However, its weight must be considered
when determining the GMW.
CaCO3.2H2O
Ca
40.1 X 1 = 40.1
C
12.0 X 1 = 12.0
O
16.0 X 3 = 48.0
H
1.0 X 4 =
4.0
O
16.0 X 2 = + 32.0
136.1 g/mol
Multiply the GMW, expressed in grams per mole, times the 1/TPIV, expressed
in moles per equivalent, used as an appropriate factor.
136.1 g
mol
-------- X -------- = 68.05 g/Eq
mol
2 Eq
c. Example. Calculate the GEW of Fe2(SO4)3.
Solution. Determine the GMW of the compound.
NOTE:
The iron in ferric sulfate is ambivalent. The term ambivalent refers to the
iron's ability to have more than one valence. In order to determine the TPIV
of this and like compounds it is necessary to examine the charge of the anion
(negative ion). The TPIV will be equal to the absolute value (integer value,
excluding the sign) of the negative charge of the anion.
MD0837
4-3