What is Yield?

Example 28.14 (Yield of a small synthesis)

$1.38\,\mathrm{g}$ of salicylic acid ($M = 138.0\,\mathrm{g}/\mathrm{mol}$), that is $0.0100\,\mathrm{mol}$, react with excess ethanoic anhydride. The maximum amount of aspirin is $0.0100\,\mathrm{mol}$, that is $0.0100 \times 180.0 = 1.80\,\mathrm{g}$. If $1.35\,\mathrm{g}$ of pure dry aspirin are obtained, $\eta = 1.35 / 1.80 = 0.75$, a yield of $75\,\%$.