2. Answer the following questions about Fe and Al compounds. (a) Fe,0,o) and Al,
ID: 1035601 • Letter: 2
Question
2. Answer the following questions about Fe and Al compounds. (a) Fe,0,o) and Al,0,0) have similar chemical properties, some simallat similar lattice energies. Give two reasoes why the lantice some similarities are due to the oxides having energies of the oxides are simalar. Use the following reactions that involve Fe and Al compounds to answer parts (b) and teh Reaction 1: Reaction 2: Fe0s)+3 H,00)-+2 Fe(OH)0) ALO?s) + 3H20(l) 2A0OHha) In basc Reaction 3: Fe(OH)) NaOa)no reaction Reaction 4: AOH))+ NaOHag)-NaANOHDdag) In acid Reaction S: F(O)+3 HCKa)FeClylag)+3 H,OD Reaction 6: AOH)+3 HClag)AlCliag)+3 H,OD Reaction 7: NaOHag)+HCllag)+AKO)+NaClKag)+H,o When heated Reaction &2 Fe(OD)FeOs)+3 H,0e) Reaction 9 2 A(OH)s)A0s)+3 H,0 A, Fe(OH) 4 x 10-38 ne (b) The Kp values for Fe(OH), and Al(OH)y are given in the table above. AL0sample of powdered ) Which ion, Fe (ag) or Al (ag), will be present in the higher concentration? Justify your answer respect to the K values provided. (ii) Write a balanced chemical equation for the dissolution reaction that results in the production of the ion that you identified in part ) (c) Students are asked to develop a plan for separating Al,0,(s) from a mixture of powdered Fe,0,(s) and powdered Al,0,(s) using chemical reactions and laboratory technigues One student proposes that Al,0yls) can be separated from the mixture by adding water to the mixture and then filtering. Explain why this approach is not reasonable. GO ON TO THE NEXT PAGE -10-Explanation / Answer
(b) molarity Fe(OH)3 = 2 x 1.0 g/88.86 g/mol x 1.0 L = 0.0225 M
molarity Al(OH)3 = 2 x 1.0 g/78 g/mol x 1.0 L = 0.0256 M
(i) As Ksp of Al(OH)3 is greater than the Ksp of Fe(OH)3, greater number of Fe3+ ions would be in solution compared to Al3+ ions.
(ii) equations,
Al(OH)3(s) <==> Al3+(aq) + 3OH-(aq)
Fe(OH)3(s) <==> Fe3+(aq) + 3OH-(aq)
(c) Separation of Al2O3 from Fe2O3 by adding water
(i) This technique is not the best. The solubility of Fe(OH)3 is lower than Al(OH)3. Not all of Al(OH)3 would be in solution and it will be a mixture of Fe(OH)3 and Al(OH)3 at all times. The separation will not work efficiently.
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