J.R. S. answered 12/12/19
Ph.D. University Professor with 10+ years Tutoring Experience
SO2 + Cl2 ==> SO2Cl2
6.11 g SO2 x 1 mol SO2/64.1 g x 1 mol SO2Cl2 / mol SO2 x 135.0 g/mol SO2Cl2 = 12.87 g SO2Cl2 theoretical yield
percent yield = actual/theoretical (x100) = 12.4 g/12.87 g (x100) = 96.3% yield