Highest density planes in fee system are: i. {110} ii. {111} iii. {100} iv. All
ID: 514255 • Letter: H
Question
Highest density planes in fee system are: i. {110} ii. {111} iii. {100} iv. All of the above. b. Cu-and Ni form solid solution because of: i. The difference in their atomic radii is less than 15% ii. They have the same crystal structures (fcc); iii. Their electronic structures are similar; iv. All of the above. c. Using the x-ray diffraction, one can find: i. The indices of the diffracting planes; ii. The crystal structure of the unknown solid; iii. The lattice parameters) of the unknown crsyatal; iv. All of the above. d. The coordination number in an ionic crystal depends on: i. The ratio of the covalent radii of the atomis; ii. The ration of the ionic radii of the ions in the crystal; iii. Electronegativity; iv. Hybridization.Explanation / Answer
a) iii){100} plane in FCC has highest density. Planar density =1/a^2 where 1 is the atom/2D repeat unit and a^2=area/2D repeat unit where a=4R/root3. Whereas planar density for {111} plane=(3*1/6)/(8R^2/root3) Thus it has highest density.
b) iv) ie all the above
For true solution the interaction of solute solvent=solute-solute=solvent-solvent.
As Cu and Ni are structurally similar they form solid solution
c)iv)All the above
X-ray is useful in finding the indices of diffracting plane, crystal structure of the unknown solid and lattice parameter of the unknown solid
d)ii) Coordination number ie the number of surrounding ions with respect to a central ion depends on the radius ratio rule. If r+/r- is small then the cation can accomodate only very few anions. But if this ratio is quite big then more number of anions can be accomodated. For example in case of coordination number 6(NaCl like) r+/r-=0.414-0.732
But for CsCl r+/r->0.732 So eight Cl- can be accomodatedby one Cs+ cation.