Ice crystallizes in a hexagonal lattice. At the low temperature at which the structure was determined, the lattice constants were `a = 4.53 Å and c = 7.41 Å` (as shown in fig). How mant `H_(2)O` molecules are contained in a unit cell ? (Density of ice = 0.92 gm/cc)

Answer

4 water molecules

Explanation

`d = (Z xxM)/(N_(0) xx " volume") rArr 0.92 = (Z xx 18)/(6.02 xx 10^(23) [(6sqrt3a^(2))/(4) xx c])`
`rArr 0.92 = (Z xx 18)/(6.02 xx 10^(23) [(6 sqrt3)/(4) xx (4.53)^(2) xx 7.41 xx 10^(-24)]) rArr Z = 4`