[hlp805]

I need help to explain why LeChatelier's Principle is important in the following test for Ca²⁺.

The test: Place two drops of SOLUTION in a tube, add two drops of 0.3M (NH₄)₂C₂O₄ and record those tubes in which precipitates form. Carefully add two drops of 3M HCl and mix well.  A white precipitate that does not completely redissolve confirms the presence of Ca²⁺.

*SOLUTION = this test was performed several times with different solutions of Mg₂₊, Ba₂₊, Sr₂₊, Ca₂₊

[Bryby]

For my understanding, Le Chateliers principle states that when a system in equilibrium is disturbed it will respond in a way that recreates the equilibrium.

Ca²⁺ acts as a Lewis Base, the addition of HCl will dissolve it. The others will not dissolve (they don't act as bases.)

Without Le Chateliers principle you wouldn't be able to distinguish these solutions from one another. Hope this helps for now, someone who knows better should be along to give you a better answer.

[Phlogiston]

For my understanding, Le Chateliers principle states that when a system in equilibrium is disturbed it will respond in a way that recreates the equilibrium.

Ca²⁺ acts as a Lewis Base, the addition of HCl will dissolve it. The others will not dissolve (they don't act as bases.)

Without Le Chateliers principle you wouldn't be able to distinguish these solutions from one another. Hope this helps for now, someone who knows better should be along to give you a better answer.

Actually Ca²⁺ would be a Lewis Acid, since it's an acid that accepts pairs of electrons.  But that's the second part- first one needs to think about equilibrium between the metal ions and oxalate (C₂O₄²⁺), and then secondarily between that product and HCl.

[Bryby]

Ahhhh I am so sorry! Disregard my comments earlier. So an acidic solution will disolve the Ca2+? I feel one would need to write the chemical equation in order to understand Le Chatelier's Principle in this problem.