Yield (reaction yield): A measure of a chemical reaction's efficiency, as a ratio of moles of product to moles of reactant. Usually expressed as a percentage.
| % Yield = | Moles of product -------------------- Moles of reactant |
General form of the equation used to compute reaction yield.
| CH3Cl | + | NaI |  | CH3I | + | NaCl | |
| Molar mass | 50.49 g mol-1 | 149.89 g mol-1 | 141.94 g mol-1 | 58.44 g mol-1 | |||
| Grams used | 10.0 grams | 10.0 grams | ----- | ---- | |||
| Moles used | 0.198 mole | 0.0667 mole | ---- | ---- | |||
| Grams produced | ---- | ---- | 5.81 grams | 3.80 grams | |||
| Moles produced | ----- | ---- | 0.0409 mole | 0.0653 mole |
In this SN2 reaction, the yield of CH3I (A reaction product) from CH3Cl (a reactant) is (moles CH3I/moles CH3Cl) x 100% = (0.0409 mole/0.198 mole) x 100% = 20.7%. Maximum theoretical yield is 100%, so this is not a very efficient reaction.
