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Identifying ions present in solution. A colourless solution is analysed to determine the cation and anion present. To separate samples of this solution various tests were carried out and the observations were recorded as follows. Turns red litmus blue
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A colourless solution is analysed to determine the cation and anion present. To separate samples of this solution various tests were carried out and the observations were recorded as follows. Turns red litmus blue Does not bubble with the addition of dilute HCl no reaction with aqueous barium nitrate a white precipitate formed when a small volume of aqueous sodium hydroxide was added and this remained when excess sodium hydroxide was added a colourless solution formed with dilute sulfuric acid Using these observations identify the cation and anion present in the solution. Write balanced equations for the precipitation reactions that occurred and for the formation of any complex ions. Link these equations to the observations recorded.
The unknown anion is OH • Identified with litmus (changes red blue) • No reaction with HCL The unknown cation is Mg2+ • White ppt with NaOH that stays with excess • Mg2+ + OH- Mg(OH)2(s) • Adding H2SO4 colourless so Mg2+
Anion • No colour change with red litmus - not CO32 or OH • No reaction when AgNO3 added - not Cl • No reaction when BaCl2 added - not SO42 • therefore anionmust be NO3, (no equations since no reactions) Cation • A white precipitate formed when a small volume of aqueous sodium hydroxide was added and dissolved when excess sodium hydroxide was added must be Pb2+ or Zn2+ or Al3+ • A white precipitate formed when a small volume of aqueous silver nitrate was added and dissolved when excess silver nitrate was added must be Pb2+ or Al3+ • a white precipitate formed with dilute sulfuric acid cation must be Pb2+ • Pb2+(aq) + 2 OH(aq) Pb(OH)2(s) lead hydroxide • Pb(OH)2(s) + 2 OH(aq) [Pb(OH)4]2(aq) • or Pb2+(aq) + 4 OH(aq) [Pb(OH)4]2(aq) • SO42(aq) + Pb2+(aq) PbSO4(s) lead sulfate
A colourless solution is analysed to determine the cation and anion present. To separate samples of this solution various tests were carried out and the observations were recorded as follows. • Turns red litmus blue • no reaction with Hydrochloric acid • a orange precipitate formed when a small volume of aqueous sodium hydroxide was added. • When a few drops of KSCN solution were added to a new sample a dark red solution formed Using these observations identify the cation and anion present in the solution. Write balanced equations for the precipitation reactions that occurred and for the formation of any complex ions. Link these equations to the observations recorded.
The unknown solution is Fe(OH)3 The unknown cation is Fe3+ • addition of NaOH produces an orange precipitate • Fe3+(aq) + 3 OH(aq) Fe(OH)3(s) • Addition of Thiocyanate produces a Blood red solution. • Fe3+(aq) + SCN(aq) [FeSCN] (aq) The unknown anion is OH • Identified with litmus (changes red blue) • No reaction with HCL
A colourless solution is analysed to determine the cation and anion present. To separate samples of this solution various tests were carried out and the observations were recorded as follows: • no effect on red litmus • no reaction with aqueous silver nitrate • no reaction with aqueous barium nitrate • a white precipitate formed when a small volume of aqueous sodium hydroxide was added and this disappeared when excess sodium hydroxide was added • a white precipitate formed with dilute sulfuric acid • a white precipitate formed when a small volume of aqueous ammonia was added and this remained in the presence of excess ammonia. Using these observations identify the cation and anion present in the solution. Write balanced equations for the precipitation reactions that occurred and for the formation of any complex ions. Link these equations to the observations recorded.
