Question

What mass of zinc oxide would be produced by the thermal decomposition of 375 grams of zinc carbonate?

Answer 1

Zinc carbonate has the chemical formula : ZnCO3 and the equation for thermal decomposition is:
ZnCO3 .................> ZnO + CO2
1 mole of ZnCO3 produces one mole of ZnO

From the periodic table:
molar mass of zinc = 65.38 gm
molar mass of carbon = 12 gm
molar mass of oxygen = 16 gm

molar mass of ZnCO3 = 65.38 + 12 + 3(16) = 125.38 gm
molar mass of ZnO = 65.38 + 16 = 81.38 gm

125.38 gm of ZnCO3 produces 81.38 gm of ZnO, therefore:
mass of ZnO in 375 gm = (375 x 81.38) / 125.38 = 243.4 gm

Based on the above calculations, the correct answer is 243 grams