Friday, 5 January 2018

he average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes 16 X 8 and 18 X 8 in the sample?

Answer :
Suppose the percentage of  
  
16

X  in given sample = x
8
:.  The percentage of  
18

X  in given sample = 100-x
8
  
 As given average atomic mass of a sample of an element X = 16.2 u

=> (16  × x /100) + [18  × (100-x) /100] = 16.2
 => (16x + 1800-18x) / 100 = 16.2
=>  (16x + 1800-18x) = 16.2 × 100
=>  -2x + 1800 = 1620
=> -2x = 1620-1800
= -2x = -180
=> x = 90

:.  The  percentage of  
16

X  in given sample = x = 90 
8

:.  The  percentage of  
16

X  in given sample = 100-x =100-90 = 10
8
 

This is an answered question from Chapter 4. Structure Of The Atom of CBSE Class 9th Science

Check for Complete Exercise Solution for Chapter 4. Structure Of The Atom | CBSE Class 9th Science

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