Question

Consider the following system at equilibrium: $$ \mathrm{NO}(g)+\mathrm{SO}_{3}(g) \Longrightarrow \mathrm{NO}_{2}(g)+\mathrm{SO}_{2}(g) $$ Indicate the effect of the following changes. (a) an increase in the concentration of NO (b) an increase in the concentration of \(\mathrm{SO}_{3}\) (c) a decrease in the concentration of \(\mathrm{NO}_{2}\) (d) an increase in the concentration of \(\mathrm{NO}_{2}\)

Short answer

The equilibrium will shift as follows: \n(a) to the right for an increase in concentration of NO \n(b) to the right for an increase in concentration of \(SO_3\) \n(c) to the right for a decrease in concentration of \(NO_2\) \n(d) to the left for an increase in concentration of \(NO_2\)

Step-by-step solution

Analyzing the effect of an increase in the concentration of NO

For an increase in the concentration of NO, the system will respond by shifting the position of equilibrium to the right to decrease the concentration of NO. Therefore, the concentration of \(NO_2\) and \(SO_2\) increases while that of \(SO_3\) decreases.

Analyzing the effect of an increase in the concentration of \(SO_3\)

For an increase in the concentration of \(SO_3\), the system will shift the position of equilibrium to the right to decrease the concentration of \(SO_3\). As a result, the concentration of \(NO_2\) and \(SO_2\) increases, while that of NO decreases.

Analyzing the effect of a decrease in the concentration of \(NO_2\)

For a decrease in the concentration of \(NO_2\), the position of equilibrium will shift to the right to increase the concentration of \(NO_2\). As a result, the concentration of \(SO_2\) increases, while the concentrations of NO and \(SO_3\) decrease.

Analyzing the effect of an increase in the concentration of \(NO_2\)

For an increase in the concentration of \(NO_2\), the system will respond by shifting the position of equilibrium to the left to decrease the concentration of \(NO_2\). Therefore, the concentration of NO and \(SO_3\) increases while the concentration of \(SO_2\) decreases.

Key concepts

Le Chatelier's Principle

Le Chatelier's principle is a cornerstone concept in chemical kinetics, guiding us through the behavior of systems in equilibrium when changes occur. Simply put, it states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium will move to counteract that change. This principle helps predict how a system at equilibrium reacts to alterations such as pressure, temperature, or concentration of reactants and products.

Applied to our exercise, when the concentration of a reactant like NO is increased, according to Le Chatelier's principle, the equilibrium will shift to reduce this added concentration, in this case, by forming more of the products NO₂ and SO₂. The principle is not just descriptive but also predictive, providing us with a pathway to manipulate the outcomes of chemical reactions by adjusting external parameters.

Equilibrium Shift

An equilibrium shift refers to the movement of a chemical system at equilibrium when it is disturbed. This distillation can cause the system to readjust in order to establish a new state of balance. Equilibrium shifts can occur in response to various changes such as alterations in concentration, pressure, or temperature. In the context of our exercise, if we increase the concentration of a reactant like SO₃, the equilibrium will shift towards the products to re-establish equilibrium, effectively increasing the production of NO₂ and SO₂. Understanding equilibrium shifts allows chemists to control reaction outcomes and is pivotal in industrial applications such as the synthesis of chemicals where yield maximization is key.

Concentration Changes

Changes in concentration play a significant role in influencing chemical equilibrium. According to the principle of mass action, the rate of a reaction is directly proportional to the product of the molar concentrations of the reactants, each raised to the power of its stoichiometric coefficient in the balanced equation. Hence, altering the concentration of one or more reactants or products will lead to a shift in equilibrium to maintain the constant state defined by the equilibrium constant.

For instance, a decrease in the concentration of a product like NO₂, as outlined in our exercise, will cause the equilibrium to shift, increasing the reaction rate of the forward reaction to produce more NO₂. Similarly, if the concentration of a product is increased, the system will react by favoring the reverse reaction to consume the excess product and restore balance.