Nitrogen has two isotopes. one has an atomic mass of 14.003
amu and a relative abundance of 99.63% while the other
isotope has an atomic mass of 15.000 amu and a relative
abundance of 0.37%. what is the average atomic mass for
nitrogen?
a
14.456 amu
b
14.778 amu
c 14.993 amu
d 14.007 amu

d= 14.007 amu

Explanation:

Abundance of N¹⁴ = 99.63%

Abundance of N¹⁵ = 0.37%

Atomic mass of N¹⁴ = 14.003 amu

Atomic mass of N¹⁵ = 15.000 amu

Average atomic mass = ?

Solution:

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

Average atomic mass = (14.003 × 99.63)+(15.000× 0.37) /100

Average atomic mass =  1395.12 + 5.55 / 100

Average atomic mass  = 1400.67/ 100

Average atomic mass = 14.007 amu.

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