Thermodynamics (Ellingham)

$\Delta G^\circ = \Delta H^\circ - T\Delta S^\circ$

For 2C + $O_{2}$ → 2CO: $\Delta S$ > 0, so $\Delta G$° decreases (becomes more negative) with ↑T, enabling carbon reduction at high temperatures.

Gold Leaching (NaCN)

$4\text{Au} + 8\text{NaCN} + 2\text{H}_2\text{O} + \text{O}_2 \rightarrow 4\text{Na[Au(CN)}_2] + 4\text{NaOH}$

Gold recovery by zinc displacement:

$2\text{Na[Au(CN)}_2] + \text{Zn} \rightarrow \text{Na}_2[\text{Zn(CN)}_4] + 2\text{Au}$

Calcination (zinc carbonate)

$\text{ZnCO}_3 \xrightarrow{\Delta, \text{limited air}} \text{ZnO} + \text{CO}_2$

Roasting (zinc blende)

$2\text{ZnS} + 3\text{O}_2 \xrightarrow{\Delta, \text{excess air}} 2\text{ZnO} + 2\text{SO}_2$

Copper Self-Reduction (Bessemer)

$2\text{Cu}_2\text{S} + 3\text{O}_2 \rightarrow 2\text{Cu}_2\text{O} + 2\text{SO}_2$

$\text{Cu}_2\text{S} + 2\text{Cu}_2\text{O} \rightarrow 6\text{Cu} + \text{SO}_2$

Iron Blast Furnace (reduction zone)

$\text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2$

$\text{CaO} + \text{SiO}_2 \rightarrow \text{CaSiO}_3 \text{ (slag)}$

Hall-Heroult (anode reaction)

$\text{C} + \text{O}^{2-} \rightarrow \text{CO}_2 + 2e^-$

Mond Process (Ni)

$\text{Ni} + 4\text{CO} \xrightarrow{330\text{–}350\text{ K}} \text{Ni(CO)}_4 \xrightarrow{450\text{–}470\text{ K}} \text{Ni} + 4\text{CO}$

Van Arkel Method (Ti)

$\text{Ti} + 2\text{I}_2 \xrightarrow{\sim870\text{ K}} \text{TiI}_4 \xrightarrow{\sim1700\text{ K, W filament}} \text{Ti} + 2\text{I}_2$

Key Numerical Data

$K_{sp}(\text{melting point reduction}) : \text{Al}_2\text{O}_3 = 2072\,°\text{C} \xrightarrow{\text{cryolite}} \sim950\,°\text{C}$