a. How are the cations Ba^2+, Ca^2+, and Sr^2+ separated from Al^3+, Cu^2+, or Br^3+?
b. How are the cations Ba^2+, Ca^2+, and Sr^2+ separated from Mg^2+?
c. What reagent is used to keep the above separation in a weakly basic condition? Why is this necessary (explain in relation to the previous question).