A substance which has face-centred cubic crystal has a density of `2.16 g cm^(-3)` and the edge lenghtof the unit cell equal to 564 pm. The molar mass of the substanceis

Options

A. `71 g "mol"^(-1)`
B. `58.35 g "mol"^(-1)`
C. `43.8 g "mol"^(-1)`
D. `36.5 g "mol"^(-1)`

Answer

B

Explanation

`rho=(NM)/(a^(3)N_(A))`
`2.16 cm^(-3) (4M)/((564xx10^(-10) cm)^(3) xx 6.023xx10^(23))`
`M=(2.16 g cm^(-3) xx (564xx10^(-10) cm)^(3) xx 6.23x10^(23))/(4)`
`=1.3xx1.48515xx10^(30) xx10^(-30) =58.35 g "mol"^(-1)`