Figure 3 shows some reactions of aqueous iron ions - AQA - A-Level Chemistry - Question 4 - 2019 - Paper 1
Question 4
Figure 3 shows some reactions of aqueous iron ions.
Solution containing Complex Ion L
Reaction 1 Na2CO3(aq) -> Precipitate J
Reaction 2 Concentrated HCl(aq) ... show full transcript
Worked Solution & Example Answer:Figure 3 shows some reactions of aqueous iron ions - AQA - A-Level Chemistry - Question 4 - 2019 - Paper 1
Step 1
Give the formula of Precipitate J and state its colour. Give an equation for Reaction 1.
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Answer
Formula of J: [Fe(OH)3(H2O)3]
Colour: Brown
Equation: 2[Fe(OH)3] + 3CO3^{2-} -> 2[Fe(H2O)6]^{3+} + 3H2O
Step 2
Give the formula of L and an equation for Reaction 2.
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Answer
Formula of L: [Fe(H2O)6]^{3+}
Equation: [Fe(H2O)6]^{3+} + Cl^{-} -> [FeCl6]^{3-}
Step 3
Suggest a reagent for Reaction 3.
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A suitable reagent for Reaction 3 would be potassium iodine (KI) or dilute hydrochloric acid (HCl).
Step 4
Give the formula of Precipitate M and state its colour.
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Answer
Formula of M: [Fe(OH)3(H2O)3]
Colour: Brown
Step 5
Describe the different shapes of complexes and show how they lead to different types of isomerism.
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Answer
Different shapes of complexes can include:
Stage 1: Shapes of complexes
Octahedral (e.g., [Co(NH3)6]^{3+})
Tetrahedral (e.g., [CoCl4]^{2-})
Stage 2: Cis and trans isomerism
Cis-Isomer (E.g., [Co(NH3)4Cl2]^{+})
Trans-Isomer (E.g., [Co(NH3)2Cl4]^{2-})
Stage 3: Optical isomerism
Optically Active isomers can be observed if two non-identical ligands are present in a square planar geometry (E.g., [PtCl2(NH3)2]).
These isomers arise from the distinct spatial arrangements of ligands around the metal center.
