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

Test for the ammonium ion, NH4+ litmus stays red: Na+ add 2 drops of dilute NaOH solution. no precipitate NH4+, Na+ add NaOH solution, heat, test gas with red litmus. litmus goes blue: NH4+ Test for the ammonium ion, NH4+ hold damp red litmus paper near end of tube to test gas that comes out warm gently

Equation needed for Merit and Excellence Explanation: The weaker base (NH4+) is releasing a proton to the stronger base (OH-). NH4+ (aq) + OH-(aq) NH3(g)+ H2O NH3 is a gas rises from hot solution turns the red litmus blue. Equation needed for Merit and Excellence

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.