Question

Why is acid more affective at changing color than temperature?

For my lab experiment, when using acids to demonstrate
CoCl2(H2O)2 + 4 H2O Co(H2O)62+ + 2 Cl-, the color turned from pink to blue. but when heating the pink solution, it turned blue as well. so why are acids more effective than temperature?

Answer 1

Because you waited while heating?

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The reaction you have is backwards. It should be:

`overbrace("Co"("H"_2"O")_6^(2+))^color(pink)"pink" + 2"Cl"^(-)(aq) rightleftharpoons overbrace("CoCl"_2("H"_2"O")_2)^(color(violet)("purple")) + 4"H"_2"O"(l) rightleftharpoons overbrace("CoCl"_4^(2-)(aq))^(color(blue)("blue")) + 6"H"_2"O"(l)`

When you add `"HCl"`, it adds `"Cl"^(-)`, which gets consumed to shift the reaction to the right, forming the bluer product by Le Chatelier's principle.

When heating the solution, which contains an endothermic reaction, heat is easier to absorb at higher temperatures... so the reaction favors the forward direction and it shifts the reaction to a new equilibrium that favors the bluer product.

Unlike `"HCl"`, the heating caused the equilibrium constant to increase.

What would happen if you cool this?