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andselisk ♦
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I was in the chemistry lab earlier this week. We were doing a qualitative experiment (no concentration given for any solution).

I added an unknown solution that contains Ba2+, Ca2+,$\ce{Ba^2+},$ $\ce{Ca^2+},$ and Mg2+$\ce{Mg^2+}$ with (NH4)2SO4,$\ce{(NH4)2SO4},$ I got barium precipitate and added (NH4)2C2O4$\ce{(NH4)2C2O4}$ and another precipitate appeared. I was told the second precipitate is Ca2+.$\ce{Ca^2+}.$

But I recall from solubility mnemonic rule, I should be able to see precipitate from both Ca2+$\ce{Ca^2+}$ and Ba2+$\ce{Ba^2+}$ after adding ammonium sulfate. Why didn't I? What are the mechanics behind this? How did Calciumcalcium just sit there as a spectator ion?

I was in the chemistry lab earlier this week. We were doing a qualitative experiment (no concentration given for any solution).

I added an unknown solution that contains Ba2+, Ca2+, and Mg2+ with (NH4)2SO4, I got barium precipitate and added (NH4)2C2O4 and another precipitate appeared. I was told the second precipitate is Ca2+.

But I recall from solubility mnemonic rule, I should be able to see precipitate from both Ca2+ and Ba2+ after adding ammonium sulfate. Why didn't I? What are the mechanics behind this? How did Calcium just sit there as a spectator ion?

I was in the chemistry lab earlier this week. We were doing a qualitative experiment (no concentration given for any solution).

I added an unknown solution that contains $\ce{Ba^2+},$ $\ce{Ca^2+},$ and $\ce{Mg^2+}$ with $\ce{(NH4)2SO4},$ I got barium precipitate and added $\ce{(NH4)2C2O4}$ and another precipitate appeared. I was told the second precipitate is $\ce{Ca^2+}.$

But I recall from solubility mnemonic rule, I should be able to see precipitate from both $\ce{Ca^2+}$ and $\ce{Ba^2+}$ after adding ammonium sulfate. Why didn't I? What are the mechanics behind this? How did calcium just sit there as a spectator ion?

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Molly_K
Molly_K
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Calcium ion and sulfate did not form precipitate

I was in the chemistry lab earlier this week. We were doing a qualitative experiment (no concentration given for any solution).

I added an unknown solution that contains Ba2+, Ca2+, and Mg2+ with (NH4)2SO4, I got barium precipitate and added (NH4)2C2O4 and another precipitate appeared. I was told the second precipitate is Ca2+.

But I recall from solubility mnemonic rule, I should be able to see precipitate from both Ca2+ and Ba2+ after adding ammonium sulfate. Why didn't I? What are the mechanics behind this? How did Calcium just sit there as a spectator ion?