A binary solid X+ Y- has a zinc blende structure with Y- ions forming the lattice and X+ ion occupying 25% tetrahedral sites. The formula of the solid is


Correct option is



In zinc blende, Y- ions form ccp lattice and have two tetrahedral sits per atom or sphere.

For the formula XY, there are four tetrahedral sites for two atoms. Thus, the 25% of tetrahedral site, ie, one tetrahedral site is occupied by X+. Therefore, the formula of the compound is XY2.



If NaCl is doped with 10–3 mol% of SrCl2, calculate the concentration of cation vacancies


The composition of a sample of wustite is Fe0.93 O. What percentage of the iron is present in the form of  Fe III?


The first order reflection of a beam of  X – rays of wavelength  from the (210) plane of a crystal of the simple cubic type, occurs at an angle of 11.290, the length of the unit cell is


A solid AB has the NaCI structure. If radius of cation A+ is 120 pm, the maximum possible value of the radius of the anion B- is


CsCl crystallizes in a cubic lattice that has a Cl- at each corner and Cs+ at the centre of the unit cell. What is the value of edge length a of the cube?  



KCI crystallises in the same type of lattice as does NaCI.


The ratio of the side of the unit cell for NaCI to that for KCI is


The unit cell of aluminum is a cube with an edge length of 405 pm. The density of aluminum is 2.70 g cm-3. The type of unit cell is


Gold (at wt. 197g mol-1) crystallises is a cubic closest packed structures (the face – centred cubic) and has a density of 19.3g/cm2. Its atomic radius is


Calcium metal crystallizes in fcc lattice with edge length 556 pm. Calculate the density (in g cm-3) of metal if it contains 0.2% Schottky defects.


Which of the following statements about amorphous solids is incorrect?