1.

The `CsCl` has cubic structure of `Cl^(-)` ions in which `Cs^(+)` in which `Cs^(+)` ion is present in the body centre of the cube. It density is `3.99g cm^(-3)`. Then length of the edge of unit cell is `:`A. `312p m`B. `412p m`C. `436 p m`D. `536p m`

Answer» Correct Answer - b
The unit cell of `CsCl` has cubic arrangement of `Cl^(-)` ions and `Cs^(+)` ion is present in the body centre of the cube. Therefore, the unit cell contains one `Cs^(+)` and one `Cl^(-)` ion, `i.e.,z=1`
Molar mass of `CsCl=168.5g mol^(-1)`
Now Density`rho=(zxxm)/(a^(3)xxN_(0))`
or `a^(3)=(1xx168.5)/(3.99xx6.023xx10^(23))`
`=7.02xx10^(-23)cm^(3)`
Let the length of edge of unit cell `=a`
`:.a^(3)=7.02xx10^(-23)cm^(-3)=70.2xx10^(-24)cm^(-3)`
or `a=4.12xx10^(-8)cm=412p m`


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