The relative atomic mass of a naturally occurring lithium consisting of 90% (^7 _3)Li and (^6 _3)10% Li is
-
A.
6.9 -
B.
7.1 -
C.
6.2 -
D.
6.8
Correct Answer: Option A
Explanation
R.A.M = m(_1 alpha_1) + m(_2 alpha_2)
= 7(90/100) + 6(10/100)
= 6.3 + 0.6
= 6.9