Question

What will produce and happen to the color if I add more NaOH in CaCl2 and ZnCl2?

Answer 1

The solution will turn from colourless to turbid white.

Explanation:

First of all, upon the addition of sodium hydroxide solution to a solution mixture of calcium and zinc chloride, a white precipitate of both calcium hydroxide Ca(OH)2 and Zn(OH)2.

Then, after adding excess of NaOH, zinc hydroxide will turn to sodium zincate Na2Zn(OH)4 which is soluble in water, hence calcium hydroxide will settle down and the solution will be clear colourless.

Here are the balanced equations:

CaCl2(aq) + 2NaOH(aq) -------> Ca(OH)2(s) + 2NaCl(aq)

ZnCl2(aq) + 2NaOH(aq) --------> Zn(OH)2(s) + 2NaCl(aq)

Zn(OH)2(s) + 2NaOH(aq)"excess" -----------> Na2Zn(OH)4(aq)