To extract gold from its ore, the ore is treated with sodium...

To extract gold from its ore, the ore is treated with sodium cyanide solution in the presence of oxygen and water. \begin{equation} 4 \mathrm{Au}(\mathrm{s})+8 \mathrm{NaCN}(\mathrm{aq})+\mathrm{O}_{2}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(1) \rightarrow \end{equation} \begin{equation} \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad4 \mathrm{NaAu}(\mathrm{CN})_{2}(\mathrm{aq})+4 \mathrm{NaOH}(\mathrm{aq}) \end{equation} \begin{equation} \begin{array}{l}{\text { a. Determine the mass of gold that can be extracted if }} \\ {25.0 \text { g of sodium cyanide is used. }} \\ {\text { b. If the mass of the ore from which the gold was }} \\ {\text { extracted is } 150.0 \mathrm{g}, \text { what percentage of the ore is gold? }}\end{array} \end{equation}

To extract gold from its ore, the ore is treated with sodium
cyanide solution in the presence of oxygen and water.
\begin{equation}
4 \mathrm{Au}(\mathrm{s})+8 \mathrm{NaCN}(\mathrm{aq})+\mathrm{O}_{2}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(1) \rightarrow
\end{equation}
\begin{equation}
\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad4 \mathrm{NaAu}(\mathrm{CN})_{2}(\mathrm{aq})+4 \mathrm{NaOH}(\mathrm{aq})
\end{equation}
\begin{equation}
\begin{array}{l}{\text { a. Determine the mass of gold that can be extracted if }} \\ {25.0 \text { g of sodium cyanide is used. }} \\ {\text { b. If the mass of the ore from which the gold was }} \\ {\text { extracted is } 150.0 \mathrm{g}, \text { what percentage of the ore is gold? }}\end{array}
\end{equation}

Key Concepts

Balanced Chemical Equation

A balanced chemical equation represents the conservation of mass in a reaction by showing that the number of atoms for each element is the same on both sides of the equation. This concept is fundamental for accurately relating the quantities of reactants and products in any chemical process.

Stoichiometry

Stoichiometry involves the quantitative relationships among reactants and products in a chemical reaction. It allows one to determine how much product can theoretically be obtained from a given amount of reactant by using the mole ratios established in the balanced equation.

Limiting Reagent

The limiting reagent is the reactant that is entirely consumed first in a chemical reaction, thereby limiting the amount of product formed. Identifying the limiting reagent is crucial for calculating the theoretical yield of the reaction.

Molar Conversions

Molar conversions are the calculations used to convert between the mass of a substance and the number of moles, utilising the molar mass as a conversion factor. These conversions are essential for linking the mass of reactants or products to the stoichiometric coefficients in a balanced chemical equation.

Percentage Composition

Percentage composition is a measure of the mass percentage of a particular element or compound within a mixture or sample. In extraction processes, it is used to determine the purity or concentration of a substance relative to the overall mass of the material.

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