Problem 36 - Chemistry Matter and Change

Question

Does the following equation represent a homogeneous equilibrium or a heterogeneous equilibrium? Explain. your answer. $$ \mathrm{H}_{2} \mathrm{O}(s) \rightleftharpoons \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) $$

Step-by-Step Solution

Answer

The given equation represents a heterogeneous equilibrium because the reactant and product are in different phases of matter: ice \(\mathrm{H}_{2} \mathrm{O}(s)\) is in the solid phase, and water \(\mathrm{H}_{2}\mathrm{O}(\mathrm{l})\) is in the liquid phase. In a homogeneous equilibrium, all reactants and products would be in the same phase.

Step 1: Identify the states of the reactants and products

Look at the given chemical equation: \[ \mathrm{H}_{2} \mathrm{O}(s) \rightleftharpoons \mathrm{H}_{2}\mathrm{O}(\mathrm{l}) \] Here, \(\mathrm{H}_{2} \mathrm{O}(s)\) represents solid water (ice) and \(\mathrm{H}_{2}\mathrm{O}(\mathrm{l})\) represents liquid water.

Step 2: Compare the states of reactants and products

We can see that the states of the substances in the reaction are different: - Ice (\(\mathrm{H}_{2} \mathrm{O}(s)\)) is in the solid phase. - Water (\(\mathrm{H}_{2}\mathrm{O}(\mathrm{l})\)) is in the liquid phase.

Step 3: Determine if the equilibrium is homogeneous or heterogeneous

Since the reactant and product are in different phases of matter, we can conclude that this equilibrium is: Heterogeneous equilibrium. A heterogeneous equilibrium involves reactants and products in different phases while in a homogeneous equilibrium, all reactants and products are in the same phase.

Key Concepts

Heterogeneous Equilibrium

In the world of chemistry, understanding the different types of equilibria is crucial for grasping how chemical reactions take place. When it comes to heterogeneous equilibrium, it involves a system where the reactants and products exist in multiple phases of matter. This differs from a homogeneous equilibrium, where all substances involved are in the same phase.

Let's consider the provided exercise as a practical example. The chemical equation \(\mathrm{H}_2 \mathrm{O}(s) \rightleftharpoons \mathrm{H}_2\mathrm{O}(\mathrm{l})\) shows water in both solid (ice) and liquid forms. Since ice and liquid water are different phases of matter, the equilibrium established between them is indeed heterogeneous.

Heterogeneous equilibrium plays a vital role in processes such as crystallization, dissolution, and even chemical reactions occurring on catalyst surfaces. This type of equilibrium obeys all the general laws of chemical equilibrium but with the added complexity of phase differences, which can affect both the rate and the position of the equilibrium.

Phases of Matter

The phases of matter are distinct forms in which different phases of matter occur. Matter typically exists in one of four states—solid, liquid, gas, and plasma—and transitions between these states can occur through physical processes. In the context of the exercise, we are particularly interested in the solid and liquid phases.

In a solid such as ice (\(\mathrm{H}_2 \mathrm{O}(s)\)), the molecules are closely packed together and vibrate in place, providing a definite shape and volume. In contrast, the liquid state (\(\mathrm{H}_2\mathrm{O}(\mathrm{l})\)) has molecules that are still close but are able to move around, leading to a definite volume but no fixed shape.

Understanding the behavior of different phases of matter is crucial for explaining various physical properties and phenomena, including the interaction between matter in different states, as seen in the process of melting or freezing water.

Chemical Reactions

The backbone of chemistry lies in chemical reactions, which are processes where substances (reactants) are transformed into different substances (products). Whether it's the simple melting of ice or the complex synthesis of pharmaceuticals, chemical reactions are fundamental to both scientific inquiry and industrial applications.

The exercise at hand focuses on a simple chemical reaction where water shifts from solid to liquid form. This particular reaction is an example of a phase change, one of the most basic types of chemical reactions. It is also reversible, indicated by the double-arrow in the chemical equation (\(\rightleftharpoons\)), which tells us that water can readily transition between solid and liquid under the appropriate conditions.

Familiarizing oneself with the various types of chemical reactions—from synthesis and decomposition to single-replacement and double-replacement—can provide a profound understanding of the natural and synthetic processes that govern our world.