Question

Electrolytes when dissolved in water dissociate into ions because : (a) They are unstable. (b) The water dissolves it. (c) The force of repulsion increases. (d) The force of electrostatic attraction is broken down by water.

Short answer

The correct answer is (d) The force of electrostatic attraction is broken down by water.

Step-by-step solution

Understand the Nature of Electrolytes

Recognize that electrolytes are compounds that, when dissolved in water, break apart into positively and negatively charged ions. This process is known as dissociation and happens because the polar water molecules interact with the ions in the electrolyte.

Evaluate the Given Options

Assess each of the given options in the context of the dissociation process of electrolytes in water. (a) 'They are unstable' is not a complete explanation since stability depends on the environment. (b) 'The water dissolves it' is incorrect as many substances dissolve in water without forming ions. (c) 'The force of repulsion increases' is not directly related to why dissociation occurs. (d) 'The force of electrostatic attraction is broken down by water' suggests that water molecules intervene between ions, weakening the electrostatic forces that hold them together in the solid, thus allowing them to separate into individual ions.

Identify the Correct Answer

The correct answer is the one that best explains the process of dissociation of electrolytes in water. In this case, it is the interaction of water molecules with the ions that breaks down the electrostatic forces holding the ions together in the solid lattice, allowing them to dissociate into individual ions.

Key concepts

Electrostatic Attraction in Electrolytes

Electrostatic attraction is the force that holds together the oppositely charged ions in an electrolyte. When electrolytes are in the solid state, this force maintains the ions in a rigid lattice structure. Upon dissolution in water, the polar nature of water molecules plays a critical role in overcoming this attraction.

Water, a 'universal solvent', has molecules with a slight positive charge on one end and a slight negative charge on the other, which allows them to surround and interact with both positive and negative ions from the electrolyte. This interaction weakens the electrostatic attraction between the ions in the lattice, resulting in a process known as dissociation. It's a fascinating phenomenon that lays the foundation for understanding conductivity and chemical reactivity in solutions, key concepts in physical chemistry, particularly for students preparing for competitive exams like the Joint Entrance Examination (JEE) for engineering in India.

Polar Water Molecules and Ions

The dissociation of electrolytes in solution is greatly influenced by the nature of water molecules. Due to their polarity, water molecules are able to encapsulate ions, stabilizing them in solution. This encapsulation is referred to as hydration when concerning ions.

Hydration of Ions

The slightly negative oxygen side of water is attracted to cations (positively charged ions), while the slightly positive hydrogen side is drawn to anions (negatively charged ions). This stabilizing effect is vital because it helps to spread the ions throughout the solution, making the substance conductive. To visualize this, picture water molecules as tiny magnets, aligning themselves around the ions according to their charges and stripping them away from the electrolyte's solid structure.

Physical Chemistry for JEE

Physical chemistry topics, such as the dissociation of electrolytes, are essential for students preparing for the JEE. Understanding these concepts is not only crucial for scoring well on the exam but also for the practical applications in engineering and the sciences.

Applications and Implications

The principles governing electrolytes and their behavior in solution are applicable in battery technology, understanding biological systems, and in various industrial processes. JEE aspirants must have a firm grasp of how electrolytes function in different environments to ace questions related to physical chemistry. This involves appreciating both the theoretical aspects, such as the role of electrostatic forces and the physical behavior of polar molecules, and also practical applications, which might include calculating the molar conductivity of a solution or the degree of dissociation for a particular electrolyte.