Number of moles of calcium ions present in 0.5 moles of  Calcium carbonate are ( NA =Avagadro's number)

One mole of CaCO3 contains….2 moles(2NA) of ions…One mole(NA) of Ca2+…One mole(NA) of CO32-;0.5 moles of CaCO3 contains….1 mole(NA) of ions…0.5 moles(0.5NA) of Ca2+…0.5 moles(0.5NA) of CO32-; CaCO3⇌Ca2++CO32- ;