Calculate the value of Avogadro number from the internuclear distance of adjacent ions in `NaCl, 0.282 nm` and the density of solid `NaCl` is `2.17xx10^(3)kg//m^(3)` . A unit cell contains `4 NaCl` formula units.

Explanation

To calculate Avogadro number, that is, number of NaCl formula units per mol, let us assume 1 mole of NaCl.
`"Volume of 1 mole of NaCI"=("mass of 1 mole")/("density")=(58.5xx10^(-3))/(2.17xx10^(3))=2.7xx10^(-5)m^(3)`
`"Volume of 1 unit cell"=a^(3)=(0.564xx10^(-9))^(3)=1.79xx10^(-28)m^(3)`
`therefore` Number of unit cells per mol `=(2.7xx10^(-5))/(2.79xx10^(-28))=1.51xx10^(23)`
Since 1 unit cell of NaCl has 4 NaCl formula units,
Avogadro number (formula units per mol) `=4xx(1.51xx10^(23))=6.04xx10^(23)`