Qualitative Analysis Cations Internal Assessment 2.1- part one
Record your results clearly First step: add 2 drops of dilute NaOH(aq) Record your results clearly
add 2 drops of dilute NaOH solution. no precipitate Na+
add 2 drops of dilute NaOH solution. add excess NaOH solution white precipitate forms Al3+, Zn2+, Pb2+, Mg2+, Ba2+ add excess NaOH solution precipitate disappears Al3+, Zn2+, Pb2+ precipitate remains Mg2+, Ba2+
Mg2+(aq) + 2 OH(aq) Mg(OH)2(s) Equations needed for Merit and Excellence white precipitate forms Al3+, Zn2+, Pb2+, Mg2+, Ba2+ Mg2+(aq) + 2 OH(aq) Mg(OH)2(s) Add the equations for the rest of the cations. Equations needed for Excellence precipitate disappears Al3+, Zn2+, Pb2+ Zn(OH)2(s) + 2 OH(aq) [Zn(OH)4]2(aq) Zn2+(aq) + 4 OH(aq) [Zn(OH)4]2(aq) Add the equations for Al3+ and Pb2+ .
add dilute H2SO4 solution Is it Mg2+ or Ba2+? precipitate remains Mg2+, Ba2+ New solution in a clean test tube!!!! add dilute H2SO4 solution colourless solution Mg2+ white precipitate Ba2+ Equation needed for Merit and Excellence SO42(aq) + Ba2+(aq) BaSO4(s)
add 2 drops, then excess NH3 solution precipitate disappears Al3+, Zn2+, Pb2+ NH3 is a base NH3 provides OH- ions in solution Write down the 3 equations for the precipitates. New solution in a clean test tube!!!! add 2 drops, then excess NH3 solution Equations needed for Merit and Excellence white precipitate forms and disappears, Zn2+ Equation needed for Excellence white precipitate forms Al3+, Pb2+ Zn(OH)2(s) + 4 NH3(aq) [Zn(NH3)4]2+ (aq) + 2 OH (aq) Zn2+(aq) + 4 NH3(aq) [Zn(NH3)4]2+(aq)
add dilute H2SO4 solution Is it Al3+ or Pb2+? white precipitate forms Al3+, Pb2+ New solution in a clean test tube!!!! add dilute H2SO4 solution Equations needed for Merit and Excellence colourless solution Al3+ white precipitate Pb2+ Pb2+(aq) + SO42(aq) PbSO4(s)
add 2 drops of dilute NaOH solution. green precipitate forms Fe2+ Equation needed for Merit and Excellence Write down the equation for this reaction.
add 2 drops of dilute NaOH solution. add 2 drops KSCN solution orange precipitate forms Fe3+ add 2 drops KSCN solution dark red solution confirms Fe3+ New solution in a clean test tube for confirmatory test Equation needed for Merit and Excellence Fe3+(aq) + 3 OH(aq) Fe(OH)3(s) Equation needed for Excellence Fe3+(aq) + SCN(aq) [FeSCN]2+(aq)
The complex ion is: [Cu(NH3)4]2+ add 2 drops of dilute NaOH solution. blue precipitate forms Cu2+ add 2 drops, then excess NH3 solution blue precipitate then deep blue solution Cu2+ New solution in a clean test tube for confirmatory test Clear solution !!!! Write down the equation for this reaction. The complex ion is: [Cu(NH3)4]2+ Equation needed for Merit and Excellence Write down the equation for this reaction. Equation needed for Excellence
The complex ion is: [Ag(NH3)2] + add 2 drops of dilute NaOH solution. brown precipitate forms Ag+ add 2 drops, then excess NH3 solution brown precipitate then colourless solution Ag+ New solution in a clean test tube for confirmatory test Clear solution !!!! Write down the equation for this reaction. The complex ion is: [Ag(NH3)2] + Equation needed for Merit and Excellence Write down the equation for this reaction.