Extracting metals and equilibria Study Guide

Metals are commonly found in the Earth's crust as compounds, often mixed with other substances within rocks called ores. To extract a pure metal from its ore, a chemical process is needed. The main chemical process for extracting most metals is called reduction. In reduction, oxygen is chemically removed from the compound, leaving the pure metal behind. For example, iron is extracted from iron ore (iron oxide) in a blast furnace by reduction with carbon, producing iron and carbon dioxide.

Ammonia (NH₃) is formed in a chemical reaction between nitrogen (N₂) and hydrogen (H₂) gases. Nitrogen is extracted from the air by fractional distillation, separating it from oxygen and other atmospheric gases. Hydrogen is mainly obtained from natural gas, commonly methane (CH₄), often through a process called steam reforming. In the ammonia synthesis reaction, nitrogen and hydrogen gases combine according to the balanced equation: N₂(g) + 3H₂(g) ↔ 2NH₃(g). The double arrow is significant because it indicates that the reaction is reversible: ammonia can break down to reform nitrogen and hydrogen. Over time, within a closed system, the rates of the forward (formation of ammonia) and reverse (decomposition of ammonia) reactions may become equal. When this occurs, the system is at dynamic equilibrium. At this point, the concentrations of all reactants and products remain constant, even though both reactions continue to occur.