Question

Example 36. A sample of strontium is found to consist
of three isotopes : 86Sr, natural abundance 9.86% ; 87Sr, natural
abundance 7.58% and 88Sr, natural abundance 82.56%. Their
relative atomic masses are 85.91, 86.91 and 87.91 respectively.
Find the atomic mass of strontium.​

Answer 1

Given:

3 isotope of strontium and their relative abundance with relative atomic mass

for 86Sr

relative abundance = 9.86%

relative atomic mass = 85.91

for 87Sr

relative abundance = 7.58%

relative atomic mass = 86.91

for 88Sr

relative abundance = 82.56%

relative atomic mass = 87.91

To Find:

the atomic mass of strontium =?

Solution:

We know that,

Total atomic mass = relative atomic mass × relative abundance

                              =  9.86%×85.91 + 7.58%×86.91  + 82.56%×87.91

                              = 8.47 + 6.58 + 72.57

                             = 87.62

Hence, the atomic mass of strontium is 87.62 u