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 Reaction of Potassium with Water

When potassium reacts with water, it produces potassium hydroxide (\( ext{KOH} \)) and hydrogen gas (\( ext{H}_2 \)). This reaction is highly exothermic, meaning it releases a significant amount of heat.

Define Exothermic Reaction

An exothermic reaction is one that releases heat to the surroundings. This increase in temperature often leads to observable effects such as an increased rate of reaction or physical changes like boiling.

Identify Characteristics in Reaction

Since the reaction of potassium with water not only generates heat but can also ignite the released hydrogen gas from the heat produced, it showcases typical traits of an exothermic reaction.

Eliminate Incorrect Options

- Hydrolysis typically involves breaking bonds using water. - Absorption involves taking in a substance, not relevant here. - Endothermic reactions absorb heat, whereas this reaction releases heat. Given these definitions, exothermic is the correct choice.

Key concepts

Reaction of Potassium with Water

When potassium (\( K \)) comes into contact with water (\( H_2O \)), an energetic reaction occurs. This reaction results in the formation of potassium hydroxide (\( KOH \)) and hydrogen gas (\( H_2 \)). The process is vigorous and rapid because potassium is a highly reactive metal, particularly with water.

During this reaction, the hydrogen gas released can ignite spontaneously due to the heat generated. This makes the reaction not only visually impressive but also an example of an exothermic reaction. The chemical equation representing this reaction is:\[ 2K + 2H_2O \rightarrow 2KOH + H_2\]

In summary, the reaction between potassium and water is not only an excellent example of a swift chemical reaction but also demonstrates the powerful nature of potassium as it reacts with water vapor and liquid. Due to the release of hydrogen gas and heat, it's essential to handle such reactions with care.

Exothermic vs Endothermic

Chemical reactions are often classified into two categories based on their heat exchange: exothermic and endothermic. Understanding these terms helps in predicting the energy changes involved in reactions.

• Exothermic Reaction: This type of reaction releases heat energy into the surroundings. An increase in temperature is often observed, causing the surroundings to feel warmer. In the case of the potassium and water reaction, the significant heat release can even ignite the hydrogen gas evolved. This demonstrates the exothermic nature.


• Endothermic Reaction: In contrast, endothermic reactions absorb heat from the surroundings. As a result, the environment may feel cooler. Examples include processes like melting ice or photosynthesis.

Thus, potassium's reaction with water is categorized as exothermic due to the release of heat, which is distinct from endothermic reactions that require heat absorption to proceed.

Concept of Hydrolysis

Hydrolysis is a term often confused with other water-related chemical processes. However, it is crucial to understand its unique definition and applications to differentiate it from reactions such as the one between potassium and water.

Hydrolysis involves breaking chemical bonds using water. Often, a larger molecule is divided into two smaller molecules with the incorporation of hydroxyl (\( OH^- \)) and hydrogen (\( H^+ \)) from water. Hydrolysis is a key reaction in biological processes, including the digestion of food where complex carbohydrates are broken down.

It is important to note that hydrolysis is not a characteristic of the potassium and water reaction. The reaction between potassium and water does not involve breaking bonds within the water molecule to form new compounds in the manner of hydrolysis. Instead, the reaction is a straightforward oxidation-reaction where a metal reacts directly with water, not involving a bond-dividing mechanism found in hydrolysis.