J.R. S. answered 04/17/19
Ph.D. University Professor with 10+ years Tutoring Experience
Al2(CO3)3 ----> Al2O3 + 3CO2
moles Al2(CO3)3 used = 58.498 g x 1 mol/233.9898 g = 0.2500 moles
moles CO2 formed = 0.2500 moles Al2(CO3)3 x 3 moles CO2/1 mole Al2(CO3)3 = 0.7500 moles CO2
mass CO2 (theoretical yield) = 0.7500 moles CO2 x 44.01 g/mole = 33.01 g CO2
% yield = actual yield/theoretical yield (x100%) = 27.68 g/33.01 g (x100%) = 83.9%