We know,
12.044×1014 PO3−4 ions = 12.0444 × 10146.022 × 1023 moles =2×10−9 moles of PO3−4 ions.
The number of electrons in one PO3−4 ion =15+(8×4)+3=50 electrons.
So, the number of moles of electrons in one mole of PO3−4 ion =50 moles
Therefore, the total number of moles of electrons in 2×10−9moles of PO3−4 ions
=50×2×10−9 moles =10−7 moles