Question

calculate average atomic mass of chlorine on the basis of data atomic number 17 mass number 35 and 37 the ratio is 3 is to 1

Answer 1

Chlorine has two isotopes namely ³⁵Cl and ³⁷Cl
³⁵Cl:³⁷Cl=3:1
Let the relative abundance of ³⁵Cl be 3x % and ³⁷Cl be x %
3x+x=100⇒4x=100⇒x=25
Relative abundance of ³⁵Cl=3×25=75%
Relative abundance of ³⁷Cl=25%
Atomic mass of chlorine=(75/100×35)+(25/100×37)
=105/4+37/4=142/4=35.5 u(Ans.)

Answer 2

ratio of isotopes=3:1

=> % of 35Cl17 = 75%

& % of 37Cl17 = 25%

relative atomic mass of Cl= 35*75/100 + 37*25/100

                                        = 35.5 u