Question
The relative atomic mass of boron (which exists in two isotopic forms ^ 10 ~B and ^ 11 ~B ) is 10.81 . What will be the abundance of ^ 10 ~B and ^ 11 ~B , respectively (consider a sample of 100 atoms)?
NDA
General Ability
General Science
2024
NDA 2024 (Phase 1)
NDA General Ability Question (2024) — Solution
Options
- A. 19 \% and 81 \%
- B. 81 \% and 19 \%
- C. 38 \% and 62 \%
- D. 62 \% and 38 \%
Answer
A. 19 \% and 81 \%
Step-by-step solution
Formula used, Average atomic mass = \% ~ abundance atomic mass total abundance aligned Let, \% ~ of B ^ 10 & =x \\ \% ~ of B ^ 11 & =100-x \\ average atomic mass & =10.81 \\ 10.81 & = x 10+(100-x) 11 100 \\ 1081 & =10 x+1100-11 x \\ -19 & =-x \\ x & =19 \\ \% ~ of B ^ 10 & =19 \% ~\\ \% ~ of B ^ 11 & =81 \% aligned
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