Gravimetric Factors

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```					                Gravimetric Factors
I. Definition
A. Suppose we perform the reactions
CaCl2 -------> Ca+2 + 2 Cl-
Ca+2 + C2O42- + H2O ------> CaC2O4 CH2O
ª              ª         ª
CaC2O4 CH2O --- --> CaC2O4 -- -->CaCO3 -- ---> CaO

B. We seek the weight of CaC2O4 C H2O but
weigh either CaCO3 or CaO

C. Gravimetric Factor- the ratio of the FW of the
substance sought to that of the substance
weighed
GF (#1)
if weigh   =    ___________________
CaO

GF (#2)
if weigh   =    ____________________
CaCO3

II. Use of The Grav. Factor
A. To Convert weight of a PPt to weight of
substance sought

#grams          # grams of
substance   =   substance    X Grav. Factor
sought          weighed

then

% Substance =
sought
sample wt
B. Example-
CaC2O4 C H2O ª CaC2O4 ª CaCO3 ª CaO
Wt of =
CaC2O4 C H2O

Wt of =
CaC2O4

Wt of =
CaCO3

Wt of =
Ca

Wt of O =
III. How to Determine Gravimetric Factors-Rule
A. Form of Graimetric Factor

B. Ensure there are the same number of
atoms of key element on the top as are on
the bottom
1. Key Element

C. Examples
1. To relate Wt of Na2CO3 to Wt Na

Key Element =

Grav. Factor =

2. To relate the Wt of BaSO4 ppt to Wt O
Key Element =

Grav. Factor =
3. To relate the Wt of KClO4 to the
weight of K2O

K2O ----------------> KClO4

Key Element =

Grav. Factor =

4. To relate the weight of Fe2O3 to the
weight of Fe3O4.

Key Element =

Grav. Factor =
5. NaClO4 ------> Na+ + ClO4-

ClO4-   ------> Cl-

Cl- + Ag+ -----> AgCl 9 Weighed

Seek Wt NaClO4 in Original

Seek Wt O in Original
IV Calculations Involving Gravimetric Factors
A. Calculate the weight of AgCl that will be
produced by the precipitation of the Cl- from
1.0000 gram of pure KCl.
B. Calculate the weight of silica (SiO2)
precipitated that would be obtained from one
gram (1.0000 g) of pure NaAl (SiO3)2
C. The phosphorous in a sample of phosphate
rock is precipitated as MgNH4PO4C6 H2O and
is ignited to Mg2P2O7. . If the ignited
precipitate weighs 0.2234 grams, calculate
the weight of MgNH4PO4C6 H2O. Also
calculate the weight of P in the original
sample.
D. The lead in a sample of ore is precipitated as
PbSO4. The dried ppt weighs 0.4264 grams.
Calculate the weight of Pb3O4 in the ore.
E. Rock containing (Pb, Fe, Cu) weighs one
gram (1.0000 g). Convert the Pb in the ore to
PbSO4 9, the Fe to Fe2O39, and the Cu to
Cu9 (electrodeposition). How would you
calculate the % Pb, % Fe, % Cu in the rock.

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Description: Gravimetric Factors