Question

Now consider an unknown that might contain AI^3+ Mn^2+ and Pb^2+. One of these three cations is easily separated from the other two forming precipitates with two different reagents that have no effect on other 2 cations. Based on this information and Part 4. decide on the first step for this separation scheme and fill in the blanks below. a. __ b. ___ c. __ d. ___ How would you separate the remaining two cations? Fill in the remaining blanks on the scheme. e. ___ f. ___ g. ____ g. What final step must be performed (involving the remaining cation at g)? What must be done to the cation at g before this final step is performed? Why?

Answer 1

This can be achieved by adding a reagent that forms a precipitate with AI3+ ion. Thus, final step for this separation scheme can be given as follows:g. Precipitation of AI3+ ion by Reagent 4. Before performing the final step, we need to remove Pb2+ ion complex from AI3+ ion precipitate by washing it with water. This is done to avoid any kind of contamination between the two precipitates.

First step for this separation scheme can be the addition of the reagent that forms a precipitate with AI3+ ion since it is easily separated from the other two cations. Thus, the first step for this separation scheme can be given as follows:a. AI3+ ion precipitated by Reagent 1.Next step can be the separation of Pb2+ ion from Mn2+ ion because Pb2+ ion is more likely to form a precipitate as compared to Mn2+ ion with the reagents used. Thus, next step for this separation scheme can be given as follows:b. Precipitation of Pb2+ ion by Reagent 2. Filtration of Pb2+ ion precipitate and separation from Mn2+ ion.To separate Mn2+ ion from the remaining cation, we need to convert it into a suitable form for further separation. Mn2+ ion can be converted into a precipitate-forming MnO2. Precipitation of MnO2 can be achieved by oxidizing Mn2+ ion with an oxidizing agent. Thus, the next step for this separation scheme can be given as follows:d. Oxidation of Mn2+ ion to MnO2 by using an oxidizing agent such as hydrogen peroxide.e. Filtration of MnO2 precipitate and separation from the remaining cation.After the Mn2+ ion has been removed, we are left with the remaining cation i.e. Pb2+ ion. It can be easily separated from other impurities by the addition of Reagent 3. Reagent 3 forms a complex with Pb2+ ion which is soluble in water. Thus, next step for this separation scheme can be given as follows:f. Formation of complex of Pb2+ ion with Reagent 3. This complex is soluble in water.g. Filtration of Pb2+ ion complex and separation from other impurities. Final step must be performed for removing the remaining cation i.e. AI3+ ion.