An aqueous solution contains a mixture of two metal-aqua ions, each with a +2 or +3 charge.
When a student adds a small amount of aqueous sodium carbonate (Na2CO3\text{Na}_2\text{CO}_3Na2CO3) to this mixture, a green precipitate forms along with bubbles of a gas that turns limewater cloudy.
When the student instead adds an excess of aqueous sodium hydroxide (NaOH\text{NaOH}NaOH) to a fresh sample of the original mixture, they observe a green precipitate and a colourless solution containing a dissolved metal complex.
Which of the following pairs of metal-aqua ions is present in the original mixture?
[Fe(H2O)6]2+[\text{Fe}(\text{H}_2\text{O})_6]^{2+}[Fe(H2O)6]2+ and [Al(H2O)6]3+[\text{Al}(\text{H}_2\text{O})_6]^{3+}[Al(H2O)6]3+
[Fe(H2O)6]2+[\text{Fe}(\text{H}_2\text{O})_6]^{2+}[Fe(H2O)6]2+ and [Fe(H2O)6]3+[\text{Fe}(\text{H}_2\text{O})_6]^{3+}[Fe(H2O)6]3+
[Cu(H2O)6]2+[\text{Cu}(\text{H}_2\text{O})_6]^{2+}[Cu(H2O)6]2+ and [Al(H2O)6]3+[\text{Al}(\text{H}_2\text{O})_6]^{3+}[Al(H2O)6]3+
[Cu(H2O)6]2+[\text{Cu}(\text{H}_2\text{O})_6]^{2+}[Cu(H2O)6]2+ and [Fe(H2O)6]3+[\text{Fe}(\text{H}_2\text{O})_6]^{3+}[Fe(H2O)6]3+
