The number of moles of magnesium needed to react with 3.0 mole of O₂ is 3 moles.
The mole is an SI unit of an atom or molecule or ion used to measure the amount of any substance. The short form for a mole is mol.
French chemist and scientist Jean Perrin named the constant in distinction to Avogadro. Since then, he was the first ones to use the constant as Avogadro constant in real to calculate number of moles.
One mole of a substance is equal to 6.022×10²³ units of that substance, wherein the substance can be atoms, molecules, or ions. it can applied universally.
3Mg + 3O₂ → 3MgO₂
It is clear from the product magnesium need 3 moles to react with oxygen.
Therefore magnesium needs 3 moles.
Learn more about a mole , here :
https://brainly.com/question/6683218
#SPJ2
