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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

          2. Adjust m & n

       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