Question

There are three naturally occurring isotopes

Answer 1

Explanation:

$^{41}\text{Hi}: 41.000\:\text{g/mol}×0.283 = 11.603\:\text{g/mol}$

$^{42}\text{Hi}: 42.000\:\text{g/mol}×0.429 = 18.018\:\text{g/mol}$

$^{44}\text{Hi}: 44.000\:\text{g/mol}×0.288 = 12.672\:\text{g/mol}$

Adding all the weighted values on the right hand side, we get

$\text{Hi}: 42.293\:\text{g/mol}$