Question

Mixing which 0.1 M aqueous solutions results in formation of a colored precipitate? A) BaCl2 and CH3COOH (B) BaCl2 and Na2CO3 (C) CuCl2 and CH3COOH (D) CuCl2 and Na2CO3 The correct answer is D but please explain I'm confused. I know that the product has to be insoluble to form a precipitate, but how do you know if it'll be colored?

Answer 1

(D) CuCl2 and Na2CO3.

Step-by-step explanation:

Hello,

In this case, we can represent the aqueous-phase reaction of D as shown below:

`CuCl_2(aq)+Na_2CO_3(aq)\rightarrow CuCO_3(s)+2NaCl(aq)`

Such precipitation of copper (II) carbonate is shown off due to its tiny solubility of 8.41x10⁻⁵ mol/L or 0.0157 g/L in water. It means that only 0.0157 grams of cupper (II) carbonate are soluble in 1 liter of water. Moreover, copper salts tend to be greenish, for that reason it is a green-colored precipitate.

Unlike the aforementioned case, the other ones do not produce colored precipitates even when barium acetate and barium carbonate are not too soluble but they are colorless. On the other hand even when copper (II) acetate is colored, it is slightly soluble in water.

Best regards.