Question

1. Would the following procedural changes cause the calculated mass percent Ni2+ ion in Ni(NH3)nCl2 to be too high, too low, or unchanged? Briefly explain each answer.

(a) A student omitted adding HCL to dissolve Ni(NH3)nCl2 before the analysis, but dissolve the Ni(NH3)nCl2 in deionized water.

Answer 1

If HCl is not added, before analysing Ni^{​​​​​2+}, some amount of Ni²⁺ will precipitate as Ni(OH)₂. To avoid this precipitation of Ni(OH)₂, HCl is always added to dissolve any Ni²⁺-salt. Thus, due to the precipitation of Ni(OH)₂, the Analysed Ni^{​​​​​2+} ion will be less than, what's actually present in the Solution, causing a Decrease in the Calculated Mass Percent of Ni^{​​​​​2+} ion in [Ni(NH₃)_n]Cl_{​​​​​2}