Question

The wrong statement among the following is (1) An exothermic reaction is that in which the reacting substances have more energy than the products. (2) Electrolysis of water is accompanied with absorption of encrgy. (3) Evaporation of water is an endothermic change. (4) The law of conservation of cnergy states that the internal cnergy of a system is constant.

Short answer

Statement (4) is incorrect.

Step-by-step solution

- Understand the Options

Carefully read each statement provided:(1) An exothermic reaction is that in which the reacting substances have more energy than the products.(2) Electrolysis of water is accompanied with absorption of energy.(3) Evaporation of water is an endothermic change.(4) The law of conservation of energy states that the internal energy of a system is constant.

- Assess the Statements

Examine each statement in isolation to determine its accuracy based on scientific principles:(1) Exothermic reactions release energy, meaning the reactants have more energy than the products, so it's correct.(2) Electrolysis of water requires energy input to break the bonds in water molecules, so it's correct.(3) Endothermic changes absorb energy, which is what happens during the evaporation of water, so it's correct.(4) The law of conservation of energy states that the total energy in a closed system remains constant, not specifically the internal energy of a system.

- Identify the Incorrect Statement

Based on the assessment, statement (4) is interpreted incorrectly. The law of conservation of energy maintains that energy cannot be created or destroyed; it can only change forms. It does not specifically state that the internal energy of a system is constant.

Key concepts

Exothermic Reactions

In an exothermic reaction, energy is released into the surroundings, usually in the form of heat. This means that the products of the reaction have less energy than the reactants. For instance, when you burn wood, it releases heat and light energy, leaving ashes that contain less energy compared to the original wood. That's why the statement 'An exothermic reaction is that in which the reacting substances have more energy than the products' is correct.
Some key features of exothermic reactions include:

• They release energy to the surroundings.
• The temperature of the surrounding environment increases.
• The enthalpy (\(\triangle H\)) change is negative.

Understanding exothermic reactions helps explain how energy is utilized and conserved in everyday chemical processes.

Electrolysis of Water

Electrolysis is a process that uses electrical energy to drive a nonspontaneous chemical reaction. In the case of water, electrolysis involves passing an electric current through water to separate it into hydrogen and oxygen gases. This process requires energy input because it breaks the chemical bonds holding the water molecules together. Thus, the statement 'Electrolysis of water is accompanied with absorption of energy' is accurate.
Steps involved in the electrolysis of water include:

• Applying an electric current.
• Breaking the bonds between hydrogen and oxygen atoms in water.
• Producing hydrogen gas at the cathode and oxygen gas at the anode.

Understanding electrolysis is crucial for applications like hydrogen fuel production and other industrial processes.

Endothermic Changes

Endothermic changes absorb energy from their surroundings. A familiar example of an endothermic change is the evaporation of water. When water evaporates, it absorbs heat energy, causing the surroundings to cool down.
Endothermic processes have the following characteristics:

• They absorb energy from the surroundings.
• The temperature of the surrounding environment decreases.
• The enthalpy (\(\triangle H\)) change is positive.

Understanding endothermic changes helps in explaining many natural processes and is essential for fields like meteorology and environmental science.

Law of Conservation of Energy

The law of conservation of energy is a fundamental principle of physics. It states that the total energy in a closed system remains constant over time; energy cannot be created or destroyed but can only change forms. Therefore, the statement 'The law of conservation of energy states that the internal energy of a system is constant' is incorrect. It's more accurate to say that the total energy within a closed system is conserved, though it may shift between different forms such as kinetic energy, potential energy, heat, etc.
Key points about the law include:

• Energy transformation (e.g., chemical energy to thermal energy).
• Maintaining balance within a closed system.
• Fundamental to understanding all energy processes.

Grasping this law is essential for fields ranging from classical mechanics to modern quantum physics.