26.7134 = mass xble + mass CaO
-26.4092 = mass xble
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00.3042 = mass CaO
Mass Ca = 0.3042 x (mass Ca/mass CaO) = 0.3042 x (40.078/56.079) = about 0.218 g Ca.
% Ca = (mass Ca/mass sample)*100 =
(0.218g/150g)*100 = 0.145% which actually is 0.145 pph (parts per 100). So just multiply top and bottom to get parts per thousand (1.45 ppt). You can convert to ppm easily from this same set up.
The calcium in a 150 mL sample of water from the Ogeechee River at a location near Savannah was determined by precipitating Ca2+ as CaC2O4.H2O (FW=146.115 g/mol). The precipitate was collected by filtration, washed and then ignited [turning the CaC2O4.H2O into CaO (FW=56.079 g/mol)] in a crucible that had an initial mass of 26.4092 g. The mass of the crucible plus CaO was 26.7134 g). What is the concentration of Ca (40.078 g/mol) in the river water in units of part per thousand (ppt) (by mass), assuming the river water has the same density as pure water?
1 answer