The edge length of NaCl unit cell is 564 pm. What is the density of NaCl ? The atomic mass of Na and Cl are 23 and 35.5 respectively. NaCL has fcc structure.

Explanation

Molar mass of `NaCl=(23+35.5)"g mol"^(-1)`
`=58.5"g mol"^(-1)`
Edge length, `a=564"pm"=5.64xx10^(-8)"cm"`
For f.c.c. structure R = 4,
`N_(A)=6.002xx10^(23)"mol"^(-1)`
`d=(AxxM)/(a^(3)xxN_(A))`
`(4xx58.5"g mol"^(-1))/((5.64xx10^(-8))"cm"^(3)xx6.022xx10^(23)"mol"^(-1))`
`=(4xx58.5xx10)/(179.41xx6.022)"g mol"^(-3)`
`=2.17"g cm"^(-3)`