EXPERIMENT 9: GROUP II CATIONS
Numeric values are not the end all and be all of chemistry experiments. Qualitative observations are equally important as indicators of chemical change and the nature of the reactants participating in a chemical reaction. In this experiment, the focus was on qualitative analysis of the Group II cations, Cu2+, Bi3+, Pb2+, Sn4+ (DePaul University, 89). Through a process of rapidly spinning the solutions in a centrifuge, adding different acids to the solutions, and analyzing the reactions of the remaining liquids and precipitates, the qualitative data in this experiment determined the presence of copper, bismuth, lead, and tin in a known and unknown solution.
In the previous week's experiment, the proper molarities of the necessary acids were prepared. The molarities of these acids include: 6 M HCl, 6 M HNO3, 6 M NH4OH, and 6 M H2SO4. To make 30 mL of 6 M HCL, 14.8
mL of the acid was added to 15.2 mL of deionized water. To make 30 mL of 6 M HNO3, 11.4 mL of the acid was added to 18.6 mL of deionized water. To make 30 mL of 6 M NH4OH, 12.0 mL of the acid was added to 18.0 mL of deionized water. Finally, to make 30 mL of 6 M H2SO4, 9.93 mL of the acid was added to 20.07 mL of deionized water. The remainders of these acidic solutions from the previous week's experiments were stored in the laboratory cabinets and used in this week's experimentations.
Refer to Figure 9.1 on Page 94 of the lab manual for the experimental procedure (DePaul University, 94). This flowchart was followed for the known sample. The flowchart was then repeated for the unknown sample. Instead of using NH3, NH4OH was used. Precisely fifteen drops of deionized water were...