Answer to Question #125575 in General Chemistry for Emily

Question

A sample of chromium contains four isotopes and has a relative atomic mass of 52.09
s the mass number and the percentage abundance of three of these isotopes.
Mass number 52 53 54
Abundance (%) 82.8, 10.9, 2.7
Determine the percentage abundance of the fourth isotope. Show by calculation that the mass number of this isotope is

Answer 1

Solution.

w(^xCr)=1-w(⁵²Cr)-w(⁵³Cr)-w(⁵⁴Cr)=1-0.828-0.109-0.027=0.036 (3.6 %)

Ar(Cr)=Ar(⁵²Cr)*w(⁵²Cr)+Ar(⁵³Cr)*w(⁵³Cr)+Ar(⁵⁴Cr)*w(⁵⁴Cr)+Ar(^xCr)*w(^xCr)

52.09=52*0.828+53*0.109+54*0.027+Ar(^xCr)*0.036

Ar(^xCr)=50

Answer: the mass number of this isotope is 50.