here is a experiment to use zn and copper chloride to determine the empirical formual of copper chloride. i do not undestand is the folloiwng step after zinc react with copper chloride (aq) add 10 drops of 1.00 mol/L of HCL to the solution? what is the purpose, it seems to make the experiment more complex.thanks.Marx
You carry out this experiment by having a solution of copper chloride. You add some zinc metal and the following reaction takes place: CuCl2 + Zn → ZnCl2 + Cu The intention is that the copper will come out of solution and it can be filtered off and dried - you can then determine the mass of copper produced But the problem is that some unconverted zinc metal may still be present which would be filtered off with the copper. this would cause an error by increasing the apparent mass of the copper produced So to prevent this you add a quantity of HCl to the reaction mixture. The HCl will readily react with the excess Zn : Zn + 2HCl → ZnCl2 + H2. The excess zinc is forced into solution as zinc chloride. But the HCl does not react with the copper. So what you filter off is only copper - no zinc contamination.
