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Qualitative analysis

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Question 1

An aqueous solution containing an unknown metal aquated cation, [M(H2O)6]n+[\text{M}(\text{H}_2\text{O})_6]^{n+}[M(H2​O)6​]n+, undergoes two sequential qualitative tests:

  1. Addition of a few drops of aqueous sodium carbonate, Na2CO3(aq)\text{Na}_2\text{CO}_3\text{(aq)}Na2​CO3​(aq), yields a brown precipitate and a colourless gas that turns limewater cloudy.
  2. Addition of a few drops of aqueous sodium hydroxide, NaOH(aq)\text{NaOH(aq)}NaOH(aq), to a fresh sample of the solution yields a brown precipitate that does not dissolve when excess NaOH(aq)\text{NaOH(aq)}NaOH(aq) is added.

Which row correctly identifies the cation [M(H2O)6]n+[\text{M}(\text{H}_2\text{O})_6]^{n+}[M(H2​O)6​]n+, the formula of the precipitate formed in reaction 1, and the identity of the gas?

Cation: [Fe(H2O)6]2+[\text{Fe}(\text{H}_2\text{O})_6]^{2+}[Fe(H2​O)6​]2+, Precipitate: FeCO3(s)\text{FeCO}_3\text{(s)}FeCO3​(s), Gas: CO2(g)\text{CO}_2\text{(g)}CO2​(g)

Cation: [Fe(H2O)6]3+[\text{Fe}(\text{H}_2\text{O})_6]^{3+}[Fe(H2​O)6​]3+, Precipitate: Fe(OH)3(s)\text{Fe(OH)}_3\text{(s)}Fe(OH)3​(s), Gas: CO2(g)\text{CO}_2\text{(g)}CO2​(g)

Cation: [Al(H2O)6]3+[\text{Al}(\text{H}_2\text{O})_6]^{3+}[Al(H2​O)6​]3+, Precipitate: Al(OH)3(s)\text{Al(OH)}_3\text{(s)}Al(OH)3​(s), Gas: CO2(g)\text{CO}_2\text{(g)}CO2​(g)

Cation: [Fe(H2O)6]3+[\text{Fe}(\text{H}_2\text{O})_6]^{3+}[Fe(H2​O)6​]3+, Precipitate: Fe2(CO3)3(s)\text{Fe}_2(\text{CO}_3)_3\text{(s)}Fe2​(CO3​)3​(s), Gas: CO2(g)\text{CO}_2\text{(g)}CO2​(g)

Qualitative analysis Questions

  1. A Level
  2. /Chemistry
  3. /Qualitative analysis