Unformatted text preview: 15 of 17 Example : The reaction of K 2 Cr 2 O 7 with FeSO 4 required one mole of K 2 Cr 2 O 7 and six moles of FeSO 4 . An electron change of six electrons occurs between one formula unit of K 2 Cr 2 O 7 and 6 formula units of FeSO 4 . Therefore: Eq wt K 2 Cr 2 O 7 = molecular wt K 2 Cr 2 O 7 (3 e- /Cr x 2 Cr/mol wt = 6 e- ) 6 Eq wt FeSO 4 = molecular wt FeSO 4 (le- /Fe x 1 Fe/mol wt = 1 e- ) 1 VII. EXAMPLES OF CONVERSIONS The following are some conversions that will be used frequently in this class. The examples use rounded atomic weights to simplify the presentation. A. Converting between meq/100 g, cmole+/kg and ppm Due to convention, most soil testing labs report ion concentrations in meq/100 g soil. It is important that we understand how to convert meq/100 g to units more commonly used in the scientific community. The System International (SI) unit to express cation exchange capacity (CEC) is cmole + /kg. Both meq/100g and cmole + /kg define the number of charges or quantity of ions per unit mass of soil, but do not quantify the mass of a particular element...
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- Spring '08
- Electron, 1 kg, Electric charge, 2 moles, 100g, 100 mole