I need help with part g. please! 2. Now consider an unknown that might contain A

Question

I need help with part g. please!

2. Now consider an unknown that might contain Al, Mn2, and Pb2 c, d One of these three cations is easily separated from the other two, forming precipitates with two different reagents that have no effect on the 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. d. How would you separate the remaining two cations? (Hint: Look carefully at the list of complex ions. One cation forms a complex in the presence of excess of a reagent that will precipitate out the other.) Fill in the remaining blanks on the scheme. g. g. What final step must be performed (involving the remaining cation at g)? Why? What must be done to the cation at g before this final step is performed? Why?

Explanation / Answer

Al+3 + Mn+2 and Pb+2

we need to add HCl so

Pb+2 + 2Cl- = PbCl(s) forms, then filer Al+3 and Mn+2

then, add

NaOH low concentration

Al3+ + 3OH- --> Al(OH)3(s) forms

Mn+2 + 2OH- ---< Mn(OH)2(s)

note that we have 2 preciptiates

so

add even more concentrated NAOH so

Aluminium forms a copmlex

Al(OH)3(s) + OH- --> Al(OH)4-(aq)

Filter Mn(OH)(s)

G is most likely Al(OH)4-

therefore, we need to bring it back to "normal"

add HCl so OH- + H+ react and form H2O(l) and Al+3 remains as cation

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