Question

The process of adsorption is (a) exothermic (b) endothermic (c) sometimes exothermic, sometimes endothermic (d) none of the above

Short answer

The answer is (a) exothermic. Adsorption is generally an exothermic process because it leads to a decrease in surface energy which is compensated by the release of heat to the surroundings.

Step-by-step solution

Understand adsorption

Adsorption refers to the process by which atoms, ions, or molecules from a substance (it could be gas, liquid or dissolved solids) adhere to a surface of an adsorbent.

Exothermic vs. Endothermic

In chemistry, the term exothermic refers to a process or reaction that releases energy from the system, usually in the form of heat, while endothermic refers to a process or reaction that absorbs energy in the form of heat.

Analyze the nature of adsorption

Adsorption is a process that occurs on the surface of an adsorbent. When the adsorbate gets adsorbed on the surface of the adsorbent, forces of attraction are established between the two. This leads to a decrease in residual forces on the surface of the solid. Hence, this process leads to a decrease in the surface energy of the adsorbent. To make up for this decrease in energy, heat is released to the surroundings, making adsorption generally an exothermic process.

Key concepts

Exothermic reactions

Exothermic reactions are chemical processes where energy is released to the surroundings, typically in the form of heat. Imagine striking a match: when it lights up, energy gets released, warming up the surroundings. During exothermic reactions, such as combustion or rusting, energy is emitted because the products have lower energy compared to the reactants.

This decrease in energy results in the release of heat, making the surroundings warmer. Additionally, certain physiological reactions in our bodies, like cellular respiration, follow this principle. It's fascinating how nature balances itself. Many processes in daily life, like burning fuel, are exothermic and provide warmth during cold days.

Endothermic reactions

Endothermic reactions, unlike exothermic ones, absorb energy from the surroundings. These reactions require external energy input to proceed. Think of cooking to understand this – like frying an egg. The heat supplied to the pan provides the energy needed to cook the egg.

Photosynthesis is another excellent example of an endothermic reaction. Plants, using sunlight, convert carbon dioxide and water into glucose and oxygen, storing energy in the process. When involved in an endothermic reaction, it'll often feel cold at first because heat energy is being used up to drive the reaction forward.

These types of reactions are crucial for processes requiring heat absorption, such as the melting of ice. Different reactions play diverse roles in nature and technology, utilizing the characteristics of endothermy to our advantage.

Surface energy

Surface energy comes into play significantly in adsorption processes, a topic you're likely exploring in your course. Picture a sponge soaking up water – molecules at the surface of a solid (like the sponge) have specific energies or surface energies.

When adsorption occurs, the instability or excess surface energy due to unbalanced forces on the surface decreases. By binding particles onto its surface, the material reduces surface energy, releasing heat.

This release usually leads the process to be exothermic. Lower surface energy makes the system more stable, akin to how balancing an object prevents it from falling. Knowing this helps in understanding technological applications like developing catalysts or purifying water, where adsorption and surface energies are finely tuned for efficiency. Understanding these concepts not only sheds light on adsorption but also on how nature intricately manages energy at surfaces.