Problem 17 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The increase of pressure on ice \(\rightleftharpoons\) water system at constant temperature will lead to (a) a decrease in the entropy of the system (b) an increase in the Gibb's energy of the system (c) no effect on the equilibrium (d) a shift of the equilibrium in the forward direction

Step-by-Step Solution

Answer

(d) a shift of the equilibrium in the forward direction.

Step 1: Understanding the equilibrium

The equilibrium described is for the phase transition of ice to water. At equilibrium, ice and water coexist, and any shift can move the equilibrium towards more ice forming or more water forming from ice.

Step 2: Concept of Le Chatelier's Principle

According to Le Chatelier's Principle, if a system at equilibrium is subjected to a change in pressure, temperature, or concentration, the system will respond by shifting its equilibrium position in such a way as to counteract the change imposed.

Step 3: Analyzing Pressure Change Effect

When pressure is increased at constant temperature, the system will favor the phase that occupies less volume. For the ice-water system, water (liquid) has a higher density and thus occupies less volume than ice (solid).

Step 4: Determine the Equilibrium Shift

Based on the analysis from Le Chatelier's Principle and the volume relationship, increasing pressure will favor the formation of water from ice and shift equilibrium towards the forward direction, which is the melting of ice to form water.

Key Concepts

Equilibrium Shift

In chemical systems, equilibrium describes a state where the rates of the forward and reverse reactions are equal, leading to constant concentrations of products and reactants. Le Chatelier's Principle is key to understanding how an equilibrium can shift. If an external change, such as pressure or temperature, is applied to a system at equilibrium, the system will adjust to counteract this disturbance. For the transition of ice to water, any changes will shift the equilibrium to favor either more ice or more water, depending on the condition applied.

This shift can be towards the forward direction, promoting the formation of more products, or in the reverse direction, leading to more reactants. It is crucial to observe the system's response under different conditions to predict this movement. When understanding equilibrium shifts, it is important to focus on the system's desire to minimize the impact of applied changes.

Phase Transition

Phase transitions involve the change of matter from one state to another, such as solid to liquid or liquid to gas. In the ice-water system, the phase transition in question is from solid ice to liquid water. At equilibrium, these phases coexist, and changing conditions decide the dominance of one phase over the other.

Understanding phase transitions, particularly in systems like this, revolves around how molecules rearrange themselves. In some cases, energy is absorbed (endothermic) or released (exothermic) to transition between phases. An increase in pressure generally leads to a preference for the phase with less volume, impacting which phase transition occurs. Ice has a larger volume compared to water, thus pressure plays a significant role in these transitions.

This understanding helps predict and control reactions in systems experiencing phase transitions under various environmental conditions.

Pressure Effect on Equilibrium

Pressure changes can dramatically affect the equilibrium of a system, especially in systems involving gases. However, in the ice to water equilibrium system, pressure still plays a critical role even though it involves a solid-liquid transition.

According to Le Chatelier's Principle, increasing pressure favors the formation of a phase that occupies less volume. In our ice-water system, water occupies less volume compared to ice due to its higher density. This means that under higher pressure, the system will shift towards forming more water, favoring the melting of ice.

Understanding this concept is particularly important in geological and industrial processes where pressure changes are common, and predicting the outcome of these changes is crucial for managing systems effectively. It highlights the intricacies involved in liquid-solid transitions and how external factors influence these balances.