A certain compound with a molar mass of 120.0 g/mol crystallizes with the sodium chloride (rock salt) structure. The length of an edge of the unit cell is 461 pm. What is the density of this compound

The density of the compound is 4.64 g/.

Explanation:

Sodium chloride crystallize as FCC face centered cubic structure. It consist of four atoms of NaCl. So the unknown compound which crytallizes like NaCl wil have volume as:

radius in fcc is calculated as

= 4r

putting the value where a is length of the edge.

= 651.9 = 4r  so r= 162.98 pm

volume is calculated by the formula:

π

putting the values,

x 3.14 x ()^3

= 4.25X 10 ^-24

1.7 X = volume of the fcc cell.

mass of the substance = 4 x 120 x 1.6605 x 10^(-24) g/u) (as it contains four atoms)

                                     = 7.9x

density =

putting the values

density =

density = 4.64 g/

the answer is c.the valence of the atoms combine .