Calculate the mass fraction of zinc in% in zinc oxide.

Given:
ZnO

To find:
ω (Zn in ZnO) -?

Decision:
1) Let’s take the amount of ZnO per 100 g;
2) Using the periodic system of D.I.Mendeleev, calculate the molar mass of ZnO, which will be numerically equal to the molecular mass:
Mr (ZnO) = Ar (Zn) + Ar (O) = 65 + 16 = 81 g / mol;
3) Find the amount of substance ZnO:
n (ZnO) = m (ZnO) / Mr (ZnO) = 100/81 = 1.23 mol;
4) Based on the definition of “amount of substance”, find the amount of substance Zn in ZnO:
n (Zn in ZnO) = n (ZnO) = 1.23 mol;
5) Find the mass of Zn:
m (Zn in ZnO) = n (Zn in ZnO) * Mr (Zn) = 1.23 * 65 = 79.95 g;
6) Find the mass fraction of Zn in ZnO:
ω (Zn in ZnO) = m (Zn in ZnO) * 100% / m solution (ZnO) = 79.95 * 100% / 100 = 79.95%.

Answer: The mass fraction of Zn in ZnO is 79.95%.