Lecture07

Lecture07 - Calculations of Gravimetric Analysis Need to...

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Calculations of Gravimetric Analysis Need to Know: Composition of substance weighed Weight of substance weighed Relationship between moles of substance weighed and moles of substance sought through balanced chemical reaction(s). Then substitute into: Moles Sought = Moles Weighed x S.R. Wt Sought m.m. Sought = Wt Weighed m.m. Weighed x S.R. Wt Sought = Wt Weighed m.m. Weighed x S.R. x m.m. Sought

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Gravimetric Stoichiometric Ratios •Balanced chemical equation. •Sequence of balanced chemical eqns. •Shortcut: If substance sought and substance weighed have an element in common other than H or O. In Stoichiometric Ratio, multiply by factors 'a' and 'b' as needed to make same number of atoms of element of interest in numerator and denominator. S.R. = "Sought" x a "Weighed" x b "Element of interest" is usually not H or O.
Example 8-2 : 1.1324 g Fe ore sample. Fe 2 O 3 xH 2 O is precipitated by addition of NH 3 . Residue ignited at high temperature to give 0.5394 g of pure Fe 2 O 3 . Calculate Wt% Fe (55.847 g/mol).

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This note was uploaded on 04/09/2008 for the course CHE 1316 taught by Professor Gipson during the Spring '08 term at Baylor.

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Lecture07 - Calculations of Gravimetric Analysis Need to...

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