the balanced equation for the decomposition of KClO₃ is as follows
2KClO₃ ---> 2KCl + 3O₂
stoichiometry of KClO₃ to O₂ is 2:3
mass of KClO₃ decomposed is - 12.3 g
number of moles of KClO₃ - 12.3 g / 122. 5 g/mol = 0.1004 mol
acccording to molar ratio
when 2 mol of KClO₃ decompose - 3 mol of O₂ is formed
therefore when 0.1004 mol of KClO₃ decompose - 3/2 x 0.1004 mol = 0.1506 mol
of O₂ is formed
mass of O₂ expected to be formed - 0.1506 mol x 32 g/mol = 4.82 g
this is the theoretical yield - 4.82 g
percentage yield = (actual yield / theoretical yield) x 100 %
actual yield = 3.20 g
theoretical yield = 4.82 g
percentage yield = (3.20 g / 4.82 g ) x 100 % = 66.4 %
percentage yield = 66.4 %