For many years the recovery of gold-that is, the separation...

For many years the recovery of gold-that is, the separation of gold from other materials-involved the use of potassium cyanide: $$4 \mathrm{Au}+8 \mathrm{KCN}+\mathrm{O}_{2}+2 \mathrm{H}_{2} \mathrm{O} \underset{4 \mathrm{KAu}(\mathrm{CN})_{2}+4 \mathrm{KOH}}{\longrightarrow}$$ What is the minimum amount of KCN in moles needed to extract $29.0 \mathrm{~g}$ (about an ounce) of gold?

For many years the recovery of gold-that is, the separation of gold from other materials-involved the use of potassium cyanide: $$4 \mathrm{Au}+8 \mathrm{KCN}+\mathrm{O}_{2}+2 \mathrm{H}_{2} \mathrm{O} \underset{4 \mathrm{KAu}(\mathrm{CN})_{2}+4 \mathrm{KOH}}{\longrightarrow}$$
What is the minimum amount of KCN in moles needed to extract $29.0 \mathrm{~g}$ (about an ounce) of gold?

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Key Concepts

Stoichiometric Ratios

Stoichiometric ratios, derived from the coefficients of a balanced chemical equation, indicate the proportions in which reactants combine and products form. They are used to calculate the minimum or required amounts of substances involved in a reaction by comparing the number of moles of one substance to another.

Balanced Chemical Equation

A balanced chemical equation displays the exact proportions of reactants and products in a chemical reaction, ensuring that the number of atoms for each element is conserved during the transformation. In problems like the extraction of gold, the coefficients in the equation indicate the mole ratios required, which are crucial for determining how much of each reactant is needed relative to another.

Mole Concept

The mole is a fundamental unit in chemistry that links the mass of a substance to the number of its constituent particles (atoms, molecules, etc.). It enables conversion between grams and moles using the substance's molar mass, making it possible to quantitatively analyze chemical reactions.

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