Question

Examples of chemical equilibrium in Nature or in our daily environment (homogeneous and heterogeneous). Can you find examples with small and large extent?

Answer 1

Example of chemical equilibrium in Nature or our daily environment-

A. Homogenous equilibrium: A homogenous equilibrium consists of all of its reactants and products in the same phase, i.e. all are in the same state of matter- either, solid, liquid, or gas.

Large scale: Diffusion of gases in the atmosphere- The atmospheric gases distribute themselves to reach an equilibrium. For example, CO₂ gases produced by a thermal power plant situated miles away from the town, reaches us through diffusion. Or, the O₂ produced by plants in our surroundings continuously diffuses in the air to establish the equilibrium. The same happened to CO₂ exhaled by us.

Small scale: Adding sugar to a glass of water also is in chemical equilibrium. Adding excess sugar causes precipitation of sugar molecules. Increasing the temperature (boiling this solution) shifts the equilibrium to the right i.e. more sugar is dissolved by increasing temperature.   

B. Heterogenous equilibrium: A heterogenous equilibrium consists of two or more of its reaction constituents in different physical states i.e. one is aqueous phase, other in gaseous phase, etc.

Large scale: Ocean water, like other water (that in you glass, or pond or lake) usually dissolves a small amount of CO₂ forming carbonic acid as follow-

H₂O + CO₂ ------> H₂CO₃ ----> H⁺ + HCO₃^-

Carbonic acid is a weak acid and it acts as buffer in aqueous solution. Change in temperature alters the equilibrium, thus can also act to alter CO₂ dissolved in oceanic water. At lower temperature, more CO₂ is dissolved in water whereas higher temperatures cause loss of CO₂ from water. Therefore, ocean is one of the major CO₂ reservoir and buffering system on Earth.

Small scale: Coffee machine can be examined as a system in equilibrium where the aqueous phase (liquid water) and gaseous phase (water vapor) exists in equilibrium while water is being boiled. Water kept in freeze at 4⁰C also is at equilibrium of its solid and liquid phase.