= 63.04 %
The balanced equation for the reaction;
5 C + 2 SO2 → CS2 + 4 CO
We can calculate the theoretical yield;
= (32.0 g SO2) / (64 g C/mol) x (1/2) x (76.1418 g CS2/mol)
= 19.035 g CS2 in theory
But;
Percentage yield = Actual yield/theoretical yield × 100%
= (12.0 g) / ( 19.035 g) × 100%
= 0.6304 × 100%
= 63.04%