To calculate the moles present in the given molecules we will apply Avogadro's number. Avogadro's number tells us that in one mole of any substance there are 6.022x10^23 molecules. Therefore if we have 4.0x10^24 molecules we will have:
![\begin{gathered} MolMgO=GivenMoleculesMgO*(1molMgO)/(6.022*10^(23)molecules) \\ MolMgO=4.0*10^24MoleculesMgO*(1molMgO)/(6.022*10^(23)molecules) \\ MolMgO=6.6molMgO \end{gathered}](https://img.qammunity.org/2023/formulas/chemistry/college/mj3xby3s75635jdoaq3wmcdf0si4zwpc4k.png)
In 4.0x10^24 particles o molecules, there are 6.6 moles of MgO