Atoms And Nuclei Question 169
Question: Atomic weight of boron is 10.81 and it has two isotopes $ _{5}B^{10} $ and $ _{5}B^{11} $ . Then ratio of $ {5}B^{10}{:{5}}B^{11} $ in nature would be [CBSE PMT 1998; JIPMER 2001, 02]
Options:
A) 19 : 81
B) 10 : 11
C) 15 : 16
D) 81 : 19
Show Answer
Answer:
Correct Answer: A
Solution:
Let the percentage of $ B^{10} $ atoms be x, then Average atomic weight $ =\frac{10x+11(100-x)}{100}=10.81 $
$ \Rightarrow x=19\ \ \ \ \therefore \frac{{N_{B^{10}}}}{{N_{B^{11}}}}=\frac{19}{81} $
