hese Tau Name: The Alkaline Earth Elements: The Metals of Group IIA 1. You were
ID: 548500 • Letter: H
Question
hese Tau Name: The Alkaline Earth Elements: The Metals of Group IIA 1. You were given an unknown which gave precipitates with all four test solutions, 1MH,So, 0.25 M (NHa)COs 1 MK,CrO, and 1 M CH,COOH and 1 M Na CO, Which of the four group II A metal cations are definitely absent from your unknown? 2. You first treated your unknown solution with 1MKC,Os and 1 M CH.COOH and a yellow precipitate formed. The liquid remaining atop this precipitate was removed after centrifugation, and to it was added 1 M H,SO No new precipitate formed. Next, a solution of 0.25 M (NH)C,O, was added to the unknown solution which had been treated in the fashion described. A white precipitate formed. This mixture was centrifuged and separated, and the clear solution was then treated with 1 M Na CO, No precipitate formed. Which metal ions were present in your unknown? Which metal ions were absent?Explanation / Answer
1) Beryllium sulfate (BeSO4) and magnesium sulfate (MgSO4) are water soluble at room temperature. Beryllium oxalate (BeC2O4) is highly water soluble while magnesium chromate (MgCrO4) is appreciably water soluble. Sulfates, oxalates, chromates and carbonates of calcium (Ca), barium (Ba) and radium (Ra) are insoluble. Hence, the salt mixture definitely didn’t contain Be2+ and Mg2+ cations.
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