Answer is: mass of zinc carbonate is 4.241 grams.
N(O) = 6.11·10²²; number of oxygen atoms.
n(O) = N(O) ÷ Na (Avogadro constant).
n(O) = 6.11·10²² ÷ 6.022·10²³ 1/mol.
n(O) = 0.101 mol; amount of oxygen atoms.
One molecule of ZnCO₃ has three oxygen atoms: n(ZnCO₃) : n(O) = 1 : 3.
n(ZnCO₃) = 0.101 mol ÷ 3.
n(ZnCO₃) = 0.034 mol.
m(ZnCO₃) = n(ZnCO₃) · M(ZnCO₃).
m(ZnCO₃) = 0.034 mol · 125.39 g/mol.
m(ZnCO₃) = 4.241 g.
