what is the minimum of amount of KCN in moles needed to extract 29 grams of gold

Answer 1

Au + 2CN^- ==> Au(CN)^-_{2</sub)
Convert 28g Au to mols. mol = grams/atomic mass.
Use the coefficients to convert mols Au to mols CN^-(KCN).
Then convert mols KCN to grams. g = mols x molar mass.}