Question

The average atomic mass of copper is `63.5`. It exists as two isotopes which are `._(29)^(63)Cu and ._(29)^(65)Cu`. Calculate the percentage of each isotope present in it.

Answer 1

Let the percentage of `._(29)^(63)Cu` isotope `= x`
`:.` The percentage of `._(29)^(65) Cu` isotope `= 100 -x`
From the above data, the average atomic mass of `Cu=(63xxx)/(100)+(65xx(100-x))/(100)`
But the given average atomic mass of `Cu = 63.5`
`:. (63xxx)/(100)+(65xx(100-x))/(100)=63.5`
`63x+6500-65x=6350" "2x=6350-6500=-150`
`2x=150orx=75`
`:.` Percentage of `._(29)&(63)Cu` isotope `= 75 %` , Percentage of `._(29)^(65) Cu` isotope `= 25 %`.