MI H2 Chem 2013 Prelim P3 Soln

201 1. 13 MI PU3 (a) Sta che    Any 1m exp (b) Tra rea dem Wh rea add On Na 3 the (i) H2 CHEM te and ex p emical prope Transition number of stability. Transition accessible from ligan d complexes Transition compounds and avail a Transition catalyst be y two for eac h planation nsition el e gents in c o monstration en aqueous ction mixt u dition of aqu the othe 3Fe(CN)6, w colour of th Explain Booklet Fe3+ + [Fe(CN ½ I2 + When F feasible  Eθ cel MISTRY PR plain in te r erties of tra metal ion s 4s and 3d e metal ion s vacant orb ds to form . metals hav s are good ability of d metals a n cause of th characte r ement com olourful dem , the followi s iron(III) s ure turned ueous sodiu r hand, w was added t he reaction n the above t. + e- Fe 2+ N)6]3- + e- e- I- Fe3+ is adde e. l = +0.23 V RELIM II PA rms of el e nsition meta s possess electrons c s form co m bitals to ac c dative bo n ve catalytic heterogen d orbitals nd their c heir ability to ristic with mplexes su c monstrations ing observa sulfate was brown. Th e um hexacya when aqu e to a fresh s mixture rem e observatio + [Fe(CN) ed to I-, the (Eθ cell > 0; r APER 3 S ectronic str u als or their variable o an be remo mplexes; th e commodate nd which r e properties; eous catal y for tempo r compounds o exist in va 1m for e ch as tho s s of redox r ations were added to aq e brown c o anoferrate(II eous sodi u ample of th mained unch ons using re Eθ = 6]4- Eθ = Eθ = e oxidation reaction is fe OLUTIONS ucture, two compounds oxidation s oved to form e ions ha v the lone p esults in t h transition m yst because rary bond are goo d riable oxida each com p se of iron reactions. In made. queous sod olour is di s I), Na4Fe(C um hexac y he aqueous hanged. elevant data = +0.77 V = +0.36 V = +0.54 V of I- to brow easible) S o characte r s. states; vari m ions of sim ve energeti c pair of elec t he formati o metals and e of the v a formation d homoge n ation states plete mat c n are com n one parti c dium iodide scharged u CN)6. yanoferrate sodium iod a from the D wn I2 by Fe 1 ristic able milar cally rons n of their cant OR nous . ching [4] mon cular , the upon (III), dide, Data e3+ is 849

2 When [Fe(CN)6]4- is added to I2, brown I2 is reduced to I-.  Eθ cell = +0.18 V (Eθ cell > 0; reaction is feasible) The oxidation of I- to brown I2 by [Fe(CN)6]3- is not feasible.  Eθ cell = -0.18 V (Eθ cell < 0; reaction is not feasible) 1m for quoting all 3 correct Eθ from Data Booklet 1m for each calculation of Eθ cell to explain observation (ii) Comment on the relative stability of the different oxidation states of iron in the presence of different ligands. Since the E θ (Fe 3+/Fe2+) is more positive compared to the E θ ([Fe(CN)6]3-/[Fe(CN)6]2-), in the presence of the CN - ligand, Fe 3+ is stabilised with respect to Fe2+. 1m for complete answer [5] (c) Haemoglobin