CHY 233: Gravimetric Analysis The calcium in a 200.0 mL sample of natural water

Question

CHY 233: Gravimetric Analysis The calcium in a 200.0 mL sample of natural water was determined by precipitating the cation as CaC,O, The precipitate was filtered, washed, and ignited in a crucible with an empty mass of 26.6002 g. The mass of the crucible plus Cao (56.077 g/mol) was 26.7134 g. Calculate the concentration of Ca (40.078 g/mol) in the water in units of g per 100 mL 1. 2. An iron ore was analyzed by dissolving a 1.1324 g sample in concentrated HCl. The resulting solution was diluted with water, and the iron(lI) was precipitated as the hydrous Fe,O, xtH,O by the addition of NH,, After filtration and washing, the residue was ignited at a high temperature to give 0.5394 g of pure Fe,O, (159.69 g/mol). Calculate... The % of Fe (55.847 g/mol) The % of Fe,04 (231.54 g/mol) in the sample a. b. Create a method for the gravimetric analysis of of cadmium in water samples

Explanation / Answer

1)

Mass CaO = Mass of crucible plus CaO Mass of empty crucible

= 26.7134 - 26.6002

= 0.1132 g CaO

56.078 g CaO contains 40.078 g of Ca

Then 0.1132 g CaO contains how much Ca

0.1132 g CaO * ( 40.078 g Ca / 56.078 g CaO)

= 0.0809021 g

0.0809021 g is present per 200 mL

then Per 100 mL water, = = 0.0004045 g/mL

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