Aqueous ions flashcard + questions
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(1a) BOTH red-brown ppts from L = Fe(H2O)3(OH)3 / Fe(OH)3 (1b) green ppt from M = Fe(H2O)4(OH)2/Fe(OH)2 for NH3 AND M = FeCO3 with Na2CO3 (1c) white ppt with L = AgCl AND white ppt with M = BaSO4 (1d) L = FeCl3 AND M = FeSO4 Stage 2 Reactions with sodium carbonate (ALLOW if any 3+ compared with any 2+) (2a) carbon dioxide is gas produced from L (could come from equation) (2b) Fe3+ / Fe(H2O)6 3+ (in L) is more acidic than Fe2+ / Fe(H2O)6 2+ (in M) ora (2c) Fe3+ is smaller / has higher charge / greater charge density of Fe3+ / is more polarising (makes ion a better proton donor) Stage 3 Equations (ECF from incorrect 3+ ion in L and/or 2+ ion in M) (3a) Fe(H2O)6 3+ + 3NH3 → Fe(H2O)3(OH)3 + 3NH4 + AND 2Fe(H2O)6 3+ +3CO3 2 - → 2Fe(H2O)3(OH)3 + 3CO2 + 3H2O (3b) Fe(H2O)6 2+ + 2NH3 → Fe(H2O)4(OH)2 + 2NH4 + AND Fe(H2O)6 2++ CO3 2 -→ FeCO3 + 6H2O OR Fe2+ + CO3 2 - → FeCO3 (3c) Ag+ + Cl- → AgCl AND Ba2+ + SO4 2 - → BaSO4
A solution containing [Fe(H2O)6] 2+ ions changes to a yellow-brown colour after several hours in contact with air. The student adds sodium carbonate to the yellow-brown solution. Give an equation for the reaction with sodium carbonate.
2 [Fe(H2O)6]3+ + 3 CO32- → 2 [Fe(H2O)3(OH)3] + 3 CO2 + 3 H2O
(c) Outline how Fe2+ ions catalyse the reaction between S2O8 2– ions and I– ions in aqueous solution. In your answer you should include * a sketch graph to show how the concentration of S2O8 2– ions changes over time * an explanation of how Fe2+ ions catalyse the reaction, including equations * an overall equation for the reaction.
https://pmt.physicsandmathstutor.com/download/Chemistry/A-level/Topic-Qs/AQA/Inorganic-II/2.6-Reactions-of-Ions-in-Aqueous-Solutions/Set-J/Reactions%20of%20Ions%20in%20Aqueous%20Solution%20MS.pdf for stage 1 for q2c stage 2 explanation 2a (reaction slow) because S2O8 2- and I- repel/high Ea OR (reaction slow) because two negative ions repel/high Ea 2b Fe2+ attracts the S2O8 2- so lower Ea OR Fe2+ and S2O8 2- oppositely charged so lower Ea 2c Iron/Fe has a variable oxidation state OR Fe2+ oxidised to Fe3+ OR Fe2+ → Fe3+ + estage 3 equations Stage3 3a 2 Fe2+ + S2O8 2- → 2 SO4 2- + 2 Fe3+ 3b 2 Fe3+ + 2 I- → 2 Fe2+ + I2 3c S2O8 2- + 2 I- → 2 SO4 2- + I2 Allow equations with hexaaqua ions
Explain the meaning of the chelate effect.
M1 When bidentate/multidentate ligands replace monodentate ligands (to form a more stable complex) M2 Because there is an increase in entropy
Addition of conc HCl to fe 2+ and fe 3+
both form yellow solutions [FeCl4]2- [FeCl4]-
Addition of conc HCl to cu
[CuCl]2- green solution
Addition of conc HCl to Al
[AlCl4]- Colourless solution