Lithium has only two naturally occurring isotopes The mass of lithium-6 is 6.01512 amu and the mass of lithium-7 is 7.01601 amu Use the atomic mass of lithium to calculate abundances mass Li 6.941?

Answer 1

The Atomic Mass of Lithium is equal to the weighted average of the two naturally occurring isotopes.

Let M=the atomc mass of Lithium; M1=the mass of lithium-6;M2=the mass of Lithium-7; %a=the abundance of lithium-6; %b=the abundance of lithium-7.

M=(M1*%a+M2*%b)/100

we know that %a and %b must add up to give us 100%, so %a=100-%b.

Therefore M=(M1*(100-%b)+M2*%b)/100

Then we just need to solve for %b because everything else is known.

M=(M1*100-M1*%b+M2*%b)/100-->M-M1=(-M1*%b+M2*%b)/100

100(M-M1)=(-M1*%b+M2*%b)-->%b=100(M-M1)/(M2-M1)=92.5%

Then %a=100-%b=100-92.5=7.5%

Answer 2

74.934%

Answer 3

7Li