NTA Abhyas JEE Main2020ChemistrySolid StatePractice
The density of KBr is 2.75 g c m - 3 , length of the unit cell is 654 pm. K = 39, Br = 80, then what can be true about the predicted nature of the solid? (Given: N A = 6.023 × 10 23 )
Options
- ASolid has face centred cubic system with co-ordination number = 6
- BSolid has simple cubic system with co-ordination number = 8
- CSolid has face centred cubic system with co-ordination number =12
- DNone of the above
Correct answer
A. Solid has face centred cubic system with co-ordination number = 6
Step-by-step solution
Given that ρ = 2.75 g c m − 3 we need to find type of unit cell ∴ ρ = Z × M N A a 3 ∵ Z = ρ × N A × a 3 M = 2.75 × 6.023 × 10 23 × ( 654 × 10 − 10 ) 3 119 ∴ Z ≃ 4 S o f c c u n i t c e l l In FCC 1 atm surrounded by 6 atoms so coordination number is 6.