Anew element was recently discovered and found to have an atomic weight of 342.38

Atomic weight of new element is 342.38 amu. The mass of lighter isotope is 340.91 amu and abundance 68.322 %.

Since, the total abundance is 100% , the abundance of heavier isotope will be (100-68.322) %=31.678%

The formula for atomic weight or average atomic weight of element is as follows:

Average atomic weight= Mass of lighter isotope×% abundance of lighter isotope+Mass of heavier isotope×% abundance of heavier isotope.

Putting the values,

Average atomic weight= 340.91×0.68322+Mass of heavier isotope×0.31678

342.38 amu=232.91+Mass of heavier isotope×0.31678

On rearranging,

Thus, mass of heavier isotope will be 345.55 amu.

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Explanation:idk