If the density of NaCl =2.165g`cm^(-3)` and the distance between `Na^(+)`and `Cl^(-)` = 281 pm,Avogadro's number is equal to

Options

A. `7times10^(23)mol^(-1)`
B. `8times10^(23)mol^(-1)`
C. `6times10^(23)mol^(-1)`
D. `4times10^(23)mol^(-1)`

Answer

C

Explanation

In an f.c.c. struccture
`a=2(r^(+)+r^(-))`
`=2times281=262"pm"`
`N_(A)=(ZtimesM)/(a^(3)timesrho)=(4times58.5)/((262times10^(-10))^(3)times2.165)`
`"6.089"times10^(23) mol^(-1)`