Problem 24 - Chemistry: Introducing Inorganic, Organic and Physical Chemistry

Question

If the following reaction was at equilibrium in a closed vessel at a controlled temperature, what would be the effect of adding more \(\mathrm{H}_{2}\) to the reaction vessel and permitting the reaction to approach equilibrium again? (Section 15.5 ) \\[ \mathrm{CO}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \rightleftharpoons \mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2}(\mathrm{g}) \\]

Step-by-Step Solution

Answer

Adding more \( \mathrm{H}_{2} \) causes the equilibrium to shift left, increasing \( \mathrm{CO} \) and \( \mathrm{H}_{2} \mathrm{O} \), and decreasing \( \mathrm{CO}_{2} \).

Step 1: Analyze the Reaction at Equilibrium

The given chemical reaction is \[ \mathrm{CO} (\mathrm{g}) + \mathrm{H}_{2} \mathrm{O} (\mathrm{g}) \rightleftharpoons \mathrm{CO}_{2} (\mathrm{g}) + \mathrm{H}_{2} (\mathrm{g}) \]. Initially, this reaction is at equilibrium, meaning the rates of the forward and reverse reactions are equal and the concentrations of reactants and products remain constant.

Step 2: Apply Le Chatelier's Principle

According to Le Chatelier's Principle, if a system at equilibrium experiences a change in concentration, temperature, or pressure, the system will adjust to counteract the effect of the change and restore a new equilibrium. In this scenario, we are adding more \( \mathrm{H}_{2} \) to the reaction vessel.

Step 3: Predict the Shift in Equilibrium

The addition of \( \mathrm{H}_{2} \) increases its concentration. According to Le Chatelier's Principle, the equilibrium will shift in a direction that alleviates this stress. Therefore, the system will shift towards the left, favoring the reverse reaction, which consumes \( \mathrm{H}_{2} \) and produces more \( \mathrm{CO} \) and \( \mathrm{H}_{2} \mathrm{O} \).

Step 4: State the Effect on Reaction Components

As a result of the equilibrium shift to the left, the concentration of \( \mathrm{CO} \) and \( \mathrm{H}_{2} \mathrm{O} \) will increase, while the concentrations of \( \mathrm{CO}_{2} \) and \( \mathrm{H}_{2} \) will decrease slightly until a new equilibrium is reached.

Key Concepts

Equilibrium

Equilibrium in a chemical reaction represents a state where the rates of the forward and reverse reactions are equal. This balance allows the concentrations of reactants and products to remain constant over time. However, it's important to note that equilibrium doesn't mean the reaction has stopped. Instead, both the forward and reverse processes occur simultaneously and at equal rates. For the reaction at hand, the equilibrium is described by the balanced chemical equation: \[ \mathrm{CO} \left(\mathrm{g}\right) + \mathrm{H}_{2} \mathrm{O} \left(\mathrm{g}\right) \rightleftharpoons \mathrm{CO}_{2} \left(\mathrm{g}\right) + \mathrm{H}_{2} \left(\mathrm{g}\right) \] In this state, neither the reactants nor the products are being consumed or produced net over time. Understanding chemical equilibrium is crucial in predicting how a system responds to external changes.

Chemical Reaction

Chemical reactions involve the transformation of reactants into products. They can be represented by chemical equations, which provide a symbolic representation of the process. In our specific case, the given reaction involves carbon monoxide (\(\mathrm{CO}\)) and water (\(\mathrm{H}_{2}\mathrm{O}\)) as reactants, forming carbon dioxide (\(\mathrm{CO}_2\)) and hydrogen gas (\(\mathrm{H}_2\)).- **Balanced Equation**: Ensures the mass and atomic numbers are conserved. - **Dynamic Process**: Continuous conversion of reactants to products and vice-versa.Understanding a reaction requires considering various factors, including the balance between energy absorbed and released, as well as the rates of the forward and reverse reactions, which determine the position of equilibrium.

Reaction Shift

The concept of a reaction shift is pivotal when analyzing how a system at equilibrium responds to changes. According to Le Chatelier's Principle, a system experiencing an external change will adjust to minimize that change and re-establish equilibrium. Let's delve into the effect of adding more hydrogen gas (\(\mathrm{H}_2\)) to the reaction vessel:- **Addition of \(\mathrm{H}_2\)**: Increases its concentration.- **Response**: The equilibrium shifts to counter the added \(\mathrm{H}_2\) by favoring the reverse reaction.- **Reverse Reaction**: Converts excess \(\mathrm{H}_2\) back into \(\mathrm{CO}\) and \(\mathrm{H}_2\mathrm{O}\), relieving the system's stress.This reaction shift signifies the system's innate balance-restoring capabilities, adhering strictly to Le Chatelier's Principle.

Concentration Changes

Concentration changes can significantly impact a system at equilibrium. When reactants or products are added or removed, the system re-adjusts to find a new balance. Here's a simplified breakdown regarding our reaction:- **Initial Equilibrium**: Stable concentrations of all components.- **Adding \(\mathrm{H}_2\)**: Increases its concentration, disrupting the balance.- **System Adjustment**: To counteract the increase in \(\mathrm{H}_2\), the system shifts left, increasing \(\mathrm{CO}\) and \(\mathrm{H}_2\mathrm{O}\).Such concentration changes prompt a new equilibrium state, continuously shaping the dynamic nature of chemical reactions under various disturbances. This underscores the importance of concentration in maintaining and predicting the behavior of chemical systems at equilibrium.