You have been given two ionic solutions, 0.10 M unknown salt, MClx solution and 0.10 M sodium soluti — Qualitative Analysis Chemistry Question
Problem Context
You have been given two ionic solutions, 0.10 M unknown salt, MClx solution and 0.10 M sodium solution, NazY. Devise and carry out an experiment to determine the identity of the unknown metal cation and the unknown anion in these solutions. The possible cations are potassium, zinc, aluminum, or silver. The possible anions are nitrate, carbonate, phosphate, or sulfide. You should provide both quantitative and qualitative evidence to support your answers.
Give a brief description of your experimental plan.
Model Answer
The plan should include both an intention to gather qualitative information about the individual solutions and the mixture and quantitative information related to the quantity of precipitate produced upon combining the two solutions.
Record your data and other observations.
Model Answer
Qualitative observations: Both solutions are clear and colorless. There is no odor from the anion solution. When mixed, a white precipitate is formed. No bubbles/gas is produced.
Quantitative observations: When the two solutions are mixed in test tubes so that the ratio of the cation and anion are varied in a systematic manner the quantity of precipitate should be greatest in the tube with a 3:2 ratio of MClx:NazY.
Calculations and Conclusions.
Model Answer
Clear MClx solution indicates the absence of Ag+ since AgCl is insoluble. Lack of odor in NazY solution indicates the absence of S2-. Appearance of precipitate indicates the absence of K+ and NO3- ions since all their compounds are soluble. Lack of bubbles in NazY solution and upon mixing indicates absence of CO32-. Possible cations are Zn2+ and Al3+ while the anion is most likely PO43-. Student provided a clear explanation of the variation of the number of drops to determine the stoichiometry ratio of MClx:NazY. Student gave a clear data table with several trials to demonstrate the 3:2 ratio of MClx:NazY. Student identified the cation as Zn2+ and the anion as PO43-.