# Why decanted solution should be colorless when determining formula of unknown chloride?

I was following the guide “Stoichiometric Determination: Empirical Formula of Copper Chloride”. Under the Procedure section the following reaction is given:

Producing solid $$\ce{Cu}$$ from a $$\ce{Cu(II)}$$ solution by reaction with $$\ce{Zn}$$.

$$\ce{\underset{(blue)}{Cu_xCl_y(aq)} + Zn(s) ->\underset{colorless}{ZnCl2(aq)} + Cu(s)}$$

If the decanted solution is not colorless, how would it affect the procedure and what does that indicate?

• If the decanted solution is not colorless (say light bluish), it means reaction is not completed and $\ce{Cu}$ ions are still in the solution. So, your calculations would be off, because it is depend on the weight of $\ce{Cu}$ metal you isolated. – Mathew Mahindaratne Jul 11 at 22:03