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.