Cyanide compounds such as sodium cyanide, NaCN, are especially useful in gold refining because they will react with gold to form a stable compound that can then be separated and broken down to retrieve the gold. Ore containing only small quantities of gold can be used in this form of "chemical mining." The equation for the reaction follows:

4Au+sNaCN+2H₂O+O₂→4NaAu(CN)₂+4NaOH

a. What percentage yield is obtained if 410 g of gold produces 540 g of NaAu