Question

Question 1.9 Calculate the atomic mass (average) of chlorine using the following data:



% Natural Abundance Molar Mass


35Cl 75.77 34.9689


37Cl 24.23 36.9659



Class XI Some Basic Concepts of Chemistry Page 22

Answer 1

The average atomic mass of chlorine
........ see the file.......





= 26.4959 + 8.9568


= 35.4527 u


    The average atomic mass of chlorine = 35.4527 u

Answer 2

concept :
$average \:atomic\: mass( \overline{A})=\sum{f_i.A_i}\\\\where,f\:shows\: percentage\:and\:A\:shows\:atomic\:mass\:of\:isotope$

now,
average atomic mass =% natural abundance of ³⁵Cl * molar mass +% natural abundance of ³⁷Cl * molar mass
= 75.77 × 34.9689/100 + 24.23 × 36.9659/100
= 26.4959 + 8.9568
= 35.4527 g/mol