Answer : The percent abundance of Li isotope-1 and Li isotope-2 is, 6.94 % and 93.1 % respectively.
Explanation :
Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.
Formula used to calculate average atomic mass follows:
.....(1)
Let the fractional abundance of Li isotope-1 be 'x' and the fractional abundance of Li isotope-2 will be '100-x'
For Li isotope-1 :
Mass of Li isotope-1 = 6.01512 amu
Fractional abundance of Li isotope-1 = x
For Li isotope-2 :
Mass of Li isotope-2 = 7.01600 amu
Fractional abundance of Li isotope-2 = 100-x
Average atomic mass of Li = 6.941 amu
Putting values in equation 1, we get:
By solving the term 'x', we get:
Percent abundance of Li isotope-1 =
Percent abundance of Li isotope-2 = 100 - x = 100-6.94 = 93.1 %