The chemical reagent of zinc oxide is produced for production by burning powdered zinc in special retorts.

The chemical reagent of zinc oxide is produced for production by burning powdered zinc in special retorts. What is the mass of zinc required to obtain 186 kg of zinc oxide?

Given:
m (ZnO) = 186 kg = 186000 g

To find:
m (Zn) -?

Decision:
1) Write down the chemical equation of the reaction:
2Zn + O2 => 2ZnO;
2) Calculate the molar masses of Zn and ZnO:
M (Zn) = Ar (Zn) = 65 g / mol;
M (ZnO) = Mr (ZnO) = N (Zn) * Ar (Zn) + N (O) * Ar (O) = 65 * 1 + 16 * 1 = 81 g / mol;
3) Calculate the amount of ZnO substance:
n (ZnO) = m (ZnO) / M (ZnO) = 186000/81 = 2296.3 mol;
4) Set the amount of Zn substance:
n (Zn) = n (ZnO) = 2296.3 mol;
5) Calculate the mass of Zn:
m (Zn) = M (Zn) * n (Zn) = 2296.3 * 65 = 149259.5 g = 149 kg.

Answer: The mass of Zn is 149 kg.