Question

A student determines the composition of a copper chloride by the procedures of this experiment. Tell whether each of the situations described below would cause the student’s experimental value for the percentage of copper in the compound to be greater than, less than, or unchanged from the theoretical value. Explain your reasoning in each case. a. The student does not add enough hydrochloric acid and some unreacted zinc remains trapped inside the copper metal. b. The student is in a hurry and beings the addition of hydrochloric acid while the solution is still blue c. The student uses 1.8 g of zinc instead of 1.5 g of zinc

Answer 1

a)

in this case student not added excess HCl, hence the zinc is still remained in the solution and we can get excess weight of CuSO₄ while weighing it.

b)

In second case, student added HCl before the the reaction of zinc and HCl. It means Zn starts reacting with HCl instead of CuSO₄. So we get less CuSO₄ measure meant while measuring.

c)

there is no change in the measuring even we added extra Zinc. Because how much CuSO₄ is there with that only Zn reacts. Therefore value is unchanged.