Question

3.7 A sample of iron oxide (wustite) has a composition Fe, 90. Its lattice parameter is found to be 4.301 Å. (a) Calculate the density of the sample (g/cm²), assuming that the nonstoichi- ometry of the compound is accounted for by vacancies on the Fe lattice. (b) Calculate the density of the sample (g/cm²), assuming that the nonstoichi- ometry of the compound is accounted for by oxygen interstitials. DATA Atomic weights Fe = 55.85 g/mol 0 = 16 g/mol FeO has a "rock salt” crystal structure (fcc) with 4 cations and 4 anions per unit cell in a perfect (defect-free) crystal.

Answer 1

o increassed the reto oxygen Jcatio decreassed. let x oxygen comos to intersatiols poin, oxgon decore now det! a per re. Feo has Nac tspe Starthe, heno & ret2 & 4 02 in one unit cell. a = 4.301 AO edse length. ♡ Formula is Fe.g30: it "g3 re anliable fore I orygen, breu Some Te is missing gh One Unitoll → Lee - the--93 a n. 4 oxygen Now, = - Axo93 lē. D= Mass of hit cell IBH Volume $X/6+ 93x9) Xs6 (413X108)3 X Guzex/z3 a = 2733 = 5.7891013 3 hoge =H4 He=1.075 is nout oxusor per te. In reo lektie 4 ste 9 orden Now, oxygen become 1.075x4 no et oxygen ber unit cell = 1.075x4 D= 4x56 + 60754 X 16 (4.3X168) 3X 6.022 X163 - 292.8 97.7 = 6.138 gro/GM3 47.7 Flaggo bornuler due to oxygen inter Sahol- - In reo one re for Belt if one o