The relative atomic mass of a naturally occurring lithium consisting of 90% 7/3 Li and 10% 6/3 Li is?

A. 6.2
B. 6.8
C. 7.1
D. 6.9

Correct Answer:

Option D = 6.9

Explanation

(90/100 x 7) + (10/100 x 6)

= 6.3 + 0.6 = 6.9