Ice crystallises in hexagonal lattice having volume of unit cell is `132times10^(-24)cm^(3)`.If density is 0.92g `cm^(3)`at a given temperature, then number of water molecules per unit cell is

Options

A. 1
B. 2
C. 3
D. 4

Answer

D

Explanation

Mass of n molecules of `H_(2)O` in hexagonal packing
`=((18g " mol"^(-1))xxn)/((6.02xx10^(23) " mol"^(-1)))`
Density `(rho)=("Mass")/("Volume")`
`(0.92 g "cm"^(-3))=((18g"mol"^(-1))xxn)/((6.02xx10^(23)"mol^(-1))xx(132xx10^(-24)cm^(3)))`
`n=((0.92 g"cm"^(-3))xx(6.02xx10^(23)"mol"^(-1))xx(132xx10^(-24)"cm"^(3)))/((18 g "mol"^(-1)))=4`