Question

How many mole of Bi atoms are needed to combine with 1.58 O atoms to make Bi2O3?

Answer 1

I assume you meant how many moles of bismuth are needed to react with `"1.58 moles"` of oxygen, right?

Well, here's the balanced chemical equation for your reaction

`4Bi_((s)) + 3O_(2(g)) -> 2Bi_2O_(3(s))`

Notice that the balanced chemical equation has 4 moles of bismuth reacting with 3 moles of oxygen to form 2 moles of bismuth (III) oxide.

What that means is that you have a `"4:3"` mole ratio between bismuth and oxygen. Since you were told that you have `"1.58 moles"` of oxygen, use the mole ratio to determine how many moles of bismuth you would need for the reaction

`"1.58 moles oxygen" * ("4 moles bismuth")/("3 moles oxygen") = "2.11 moles Bi"`

If you're interested in how many actual atoms of bismuth you'd need, use Avogadro's number to go from moles to atoms

`"2.11 moles Bi" * (6.022 * 10^(23)"atoms of Bi")/("1 mole Bi") = 1.27 * 10^(24)"atoms"`