? – To precipitate their Group C cation- Ca, Ba,
Sr a fellow student adds 1M (NH4)2SO4 and no precipitate forms. The student then
adds saturated ammonium oxalate and a white precipitate forms. What is the most likely identity of the Group C cation?
What would you instruct the student to do to confirm the identity? Specific instructions along with observations are needed.
Background Chemistry and Discussion
After removing the Group A and Group B cations from your unknown by precipitation, the Group C and D cations remain in
solution. The three ions; Ca2+, Sr2+ and Ba2+, that make up Group C have soluble chlorides and hydroxides that are reasonably
soluble in ammonia solutions. These three ions can be separated from the Group D ions by selective precipitation.
Identification of your Group C cation based solely upon the color of the precipitate formed is not possible since the
precipitates formed by Ca2+, Sr2+ and Ba2+ do not have colors unique from each other. Identification can be achieved by using
a combination of solubility behavior and flame tests. You are required to develop a scheme that will allow you to separate
and correctly identify the Group C cation present in your unknown solution.