Element X has two naturally occurring isotopes, 65X (isotopic mass 65.3410 amu, abundance 31.87%) and 67X (isotopic mass 66.9519 amu, abundance 68.13%). Calculate the atomic mass of element X.

Explanation:

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In this case, according to the given information for this problem, it turns out possible for us to calculate the average atomic mass of the element by multiplying the mass of each isotope by its percent abundance and then add up the results, just as shown below:

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number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

the answer would be a