Question

Explain The element lithium has two common isotopes: Li–6 and Li–7 If the average atomic mass of lithium is 6.94004 u, determine its percent isotopic step by step please urgently

Answer 1

Answer:

%Li-6 = 5.996% & %Li-7 = 94.004%

Explanation:

let X₁ = Li-6 & X₂ = Li-7 where Xₙ = mole fraction

X₁ + X₂ = 1 => X₁ = 1 - X₂

6·X₁ + 7·X₂ = 6.94004

=> 6(1 - X₂) + 7·X₂ = 6.94004

=> 6 - 6·X₂ + 7·X₂ = 6.94004

=> 6 + X₂ = 6.94004

X₂ = 6.94004 - 6 = 0.94004 => %X₂ = %Li-7 = 94.004%

X₁ = 1.00000 - 0.94004 = 0.05996 => %X₁ = %Li-6 = 5.996%