How do you calculate purity-adjusted reaction percent yield?
Short answer
Multiply recovered product mass by its purity fraction to estimate pure product mass, then divide by theoretical product mass. Nine grams recovered at 98 percent purity contains 8.82 grams of pure product. Against a theoretical yield of 10 grams, the purity-adjusted yield is 88.2 percent. Keep the theoretical basis and purity measurement separate from the arithmetic.
With theoretical mass B11, measured mass C11, and purity D11, pure mass is =C11*D11 and yield is =IF(B11<=0,"",E11/B11) displayed as a percentage.
Should a yield above 100 percent be capped?
Keep it visible and investigate the mass, purity, and theoretical basis. Capping the result hides the discrepancy and does not identify whether contamination, measurement, or assumptions explain it.