Question

Lithium-6 is 7% abundant and Lithium-7 is 93% abundant. What is the average atomic mass with the correct significant figures?

O 7 amu
O 6.9 amu
O 6.93 amu
O 6 amu

Answer 1

Average atomic mass = 6.93 amu.

Step-by-step explanation:

Given data:

Percent abundance of lithium -6 = 7%

Percent abundance of lithium - 7 = 93%

Average atomic mass of Li = ?

Solution:

Average atomic mass = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass) / 100

Average atomic mass = (7×6)+(93×7) /100

Average atomic mass = 42+ 651 / 100

Average atomic mass = 693/ 100

Average atomic mass = 6.93 amu.