89) KF has NaCl sructure with edge length 537.5 x 10⁻¹² m. What is the distance between K⁺ and F⁻ in KF, if density is 2.48 gm⁄cc?

90) An alloy of Cu, Ag and Au is found to have copper constituting ccp lattice. If silver atoms occupy the edge centers and gold is present at body centers, the alloy has the formula:

91) In a cubic packed structure of mixed oxides, the lattice is made up of oxide, one fifth of tetrahedral voids are occupied by divalent ions (A²⁺), while one half of the octahedral voids are occupied by trivalent ions (B³⁺), then the formula of the oxide is:

92) The number of atoms in 100 gm of a fcc crystal with density, d = 10 gm⁄cc and cell edge as 200 pm is equal to:

93) The compound ZnFeSO₄ is: