Question

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Chemical disequilibrium is likely to be present in all the following places except in (a) volcanic vents on ocean floors; (b) solid ice exposed to the extreme cold of space; (c) underground aquifers where thin films of liquid water move over rock.

Short answer

(b) Solid ice exposed to the extreme cold of space is likely in chemical equilibrium.

Step-by-step solution

Understanding Chemical Disequilibrium

Chemical disequilibrium occurs when a system is not in a stable state, often due to energy inputs or the movement of substances. This can happen naturally in environments where chemicals react with each other or where energy is continually supplied, such as near sources of heat or energy.

Analyzing the Options

Let's analyze the given locations: (a) Volcanic vents on ocean floors: These are areas with high thermal activity and varying chemical compositions due to the release of gases and minerals, indicating chemical reactions are likely. (b) Solid ice exposed to extreme cold in space: Here, temperatures are so low that chemical reactions are minimal, suggesting stability instead of disequilibrium. (c) Underground aquifers: These have moving liquid water, which interacts with rocks, providing opportunities for reactions and thus potential disequilibrium.

Identify the Exception

Given that chemical reactions typically require energy or interaction to occur, the solid ice exposed to the extreme cold of space lacks the necessary conditions for ongoing reactions. The cold, inert nature of ice in space minimizes active chemical processes, leading to equilibrium rather than disequilibrium.

Conclusion

The chemical disequilibrium is likely absent in solid ice exposed to the extreme cold of space due to its stable and unreactive conditions.

Key concepts

Volcanic Vents

Volcanic vents on the ocean floor are fascinating environments where chemical disequilibrium is the norm rather than the exception. These vents, often called hydrothermal vents, are located in areas where tectonic plates are diverging or converging.

The heat from the Earth's interior causes water to be expelled from these vents, bringing with it a variety of dissolved minerals and gases such as hydrogen sulfide.
This creates a unique chemical broth that continually changes as new materials are spewed out. As a result, numerous chemical reactions occur, driven by:

• High temperatures, which increase the rate of chemical reactions.
• The presence of dissolved minerals, which can react with seawater.
• Energy availability from the Earth’s geothermal activity.

These conditions make volcanic vents hotspots for chemical disequilibrium, as the constant flux of materials and energy promotes ongoing chemical transformations.
This environment supports unique ecosystems, hosting organisms that thrive on chemical energy rather than sunlight.

Underground Aquifers

Underground aquifers are subsurface layers of rock, sand, or gravel containing water. They play a crucial role in maintaining chemical disequilibrium.

These aquifers are dynamic systems where water moves slowly through porous rock or sediment, continuously interacting with minerals. This movement allows for a series of chemical reactions to take place. Some key factors contributing to chemical disequilibrium in aquifers include:

• The flow of water, which promotes the dissolution and transportation of minerals.
• The presence of varying mineral compositions that can react differently with the moving water.
• Atmospheric gases may dissolve in the water, further contributing to chemical complexity.

Such interactions often alter the chemical makeup of the water, leading to a non-equilibrium state. This disequilibrium can affect water's quality, making it rich in minerals, and can also influence the types of microorganisms capable of inhabiting these aquifers.

Extreme Cold of Space

The extreme cold of space presents a stark contrast to the dynamic environments of volcanic vents and aquifers. In the vastness of space, particularly on the surfaces of celestial bodies covered in solid ice, chemical reactions are heavily suppressed.

Temperatures in these regions are exceedingly low, often near absolute zero. These conditions make molecules almost inert, meaning they have very minimal kinetic energy to engage in chemical reactions. As a result, the substance remains stable over long periods, maintaining a state of chemical equilibrium.
Key reasons for this stability include:

• The absence of heat, which is necessary to increase reaction rates.
• Lack of liquid water or other solvents to facilitate reactions.
• Minimal external energy inputs to drive chemical changes.

Without these factors, the ice remains unreactive, preserving its chemical composition. Hence, while space is filled with mysteries, the extreme cold ensures that many icy bodies remain chemically inert, maintaining a stable state rather than experiencing chemical disequilibrium.