Can you help me with identification of the cation in my unknown?

[匿名]

2016-06-15 9:04 am

Ba2+, Sr2+ and Ca2+ were possible cations. We each had one of these. To the separated supernatant of a previous step, I added (NH4)2SO4 and the solution remained clear - nothing happened. When I added (NH4)2C2O4, a white precipitate quickly formed.

Because of this, I assumed that I had Calcium ion. However, my flame test looked more like Strontium...it was a pretty reddish-pink. Apparently, Calcium looks orange with a flame test.

I'm supposed to identify which cation I had but am conflicted...Please help.

回答 (1)

fooks

2016-06-15 11:54 am

All of BaC₂O₄, SrC₂O₄ and CaC₂O₄ are insoluble in water. When (NH₄)₂C₂O₄ is added, all of Ba²⁺, Sr²⁺ and Ca²⁺ ions can form white precipitates rapidly. Therefore, your induction that you had calcium ion is incorrect.

Refer to the result of flame test, you had strontium ion (Sr²⁺).

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