Question

Reaction of potassium with water is: (a) Hydrolysis (b) Absorption (c) Exothermic (d) Endothermic

Short answer

The reaction of potassium with water is exothermic.

Step-by-step solution

Understand the Chemical Reaction

The reaction of potassium (K) with water (H2O) can be described by the equation: \[ 2K + 2H_2O ightarrow 2KOH + H_2 \]This reaction produces potassium hydroxide (KOH) and hydrogen gas (H2) as products.

Determine the Nature of Reaction

In the reaction, hydrogen gas is released which indicates that heat is generated. Such reactions that release heat are characterized as exothermic processes.

Choose the Correct Option

Among the given options, recognize options (c) and (d), which relate to thermal changes. Since the reaction releases heat, the correct description is 'Exothermic'.

Key concepts

Exothermic Reactions

In chemistry, exothermic reactions are processes that release energy in the form of heat or light. When a chemical reaction occurs, bonds between atoms are broken and formed. If the energy released by forming new bonds is greater than the energy required to break the old bonds, the reaction is exothermic. For instance, the reaction of potassium with water is exothermic because the released energy exceeds the energy needed to break bonds, resulting in the release of heat. These reactions are significant because they are often self-sustaining once initiated. Examples include combustion, where substances react with oxygen, releasing heat, and cellular respiration, which releases energy in living organisms.

Key characteristics of exothermic reactions include:

• Heat release: Observable increase in temperature of the surroundings.
• Light emission: Some reactions may emit light as they release energy.
• Exothermic equation: Typically represented with products having lower energy than reactants.

Understanding exothermic reactions is crucial for safety, as they can lead to hazards if not properly managed, especially in industrial or laboratory settings.

Reactions of Metals with Water

Metals can react with water under certain conditions, with the reaction type depending on the metal's reactivity. Highly reactive metals, like potassium, react vigorously with water, often producing hydrogen gas and hydroxides. For instance, when potassium reacts with water, the reaction is immediate and generates potassium hydroxide and hydrogen gas. This can be expressed by the equation: \[ 2K + 2H_2O \rightarrow 2KOH + H_2 \].

Such reactions are typically exothermic, as they release energy. The level of metal reactivity influences how vigorously the reaction occurs. Alkali metals, located in Group 1 of the periodic table, react most intensively with water.

• Vigorous metal-water reactions: Result in significant heat and hydrogen gas release.
• Product formation: Metal hydroxides, which are typically basic.
• Reactive metals: Include potassium, sodium, and lithium.

Being aware of the reactivity of different metals with water helps in predicting the outcome of such interactions and ensures proper handling and safety precautions are taken.

Thermodynamics in Chemistry

Thermodynamics is a branch of physical science that studies energy and its transformations. In chemistry, it focuses on how energy changes during reactions and how these changes influence chemical behavior. The concept of energy conservation underpins thermodynamics, asserting that energy cannot be created or destroyed, only transformed.

Key thermodynamic principles include:

• The First Law of Thermodynamics: Energy is conserved in chemical processes.
• Enthalpy: A measurement of heat change in reactions, vital for understanding exothermic and endothermic processes.
• Entropy: A measure of disorder or randomness, with systems naturally progressing towards greater entropy.

Thermodynamics helps predict reaction spontaneity and feasibility, contributing to fields like biochemistry, physics, and engineering. For example, developing batteries and engines relies heavily on thermodynamic principles to maximize energy efficiency and performance. Mastering these concepts allows for better manipulation of chemical reactions to achieve desired energy outputs in practical applications.