Question

The synthesis of \(\mathrm{CaCO}_{3}\) uses this chemical reaction. \(\mathrm{CaO}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{~g}) \rightleftarrows \mathrm{CaCO}_{3}(\mathrm{~s})+180 \mathrm{~kJ}\) Identify three stresses that can be imposed on the equilibrium to maximize the amount of \(\mathrm{CaCO}_{3}\).

Short answer

Increase \\(\mathrm{CaO}\\) or \\(\mathrm{CO}_2\\), decrease temperature, and increase pressure.

Step-by-step solution

Understanding the Reaction

The reaction given is an exothermic reaction that forms calcium carbonate (\(\mathrm{CaCO}_3\)) from calcium oxide (\(\mathrm{CaO}\)) and carbon dioxide (\(\mathrm{CO}_2\)). The equation is: \(\mathrm{CaO} + \mathrm{CO}_2 \rightleftarrows \mathrm{CaCO}_3 + 180 \mathrm{~kJ}\). Since heat is released, it is part of the products.

Le Chatelier's Principle

According to Le Chatelier's Principle, if a stress is applied to a system at equilibrium, the system will change to counteract that stress and re-establish equilibrium. In this context, stresses include changes in concentration, pressure, and temperature.

Stress 1: Adding Reactants

Increase the concentration of \(\mathrm{CaO}\) or \(\mathrm{CO}_2\). This will push the equilibrium to the right, favoring the production of more \(\mathrm{CaCO}_3\) as the system tries to consume the added reactants.

Stress 2: Decreasing Temperature

Since the reaction is exothermic, lowering the temperature will favor the forward reaction, as the system tries to produce more heat (hence more \(\mathrm{CaCO}_3\)) to counteract the temperature drop.

Stress 3: Increasing Pressure

By increasing the pressure, especially for reactions involving gases, the equilibrium will shift towards the side with fewer gas molecules. In this case, though both sides have the same amount of gas particles, increasing the pressure can still push the equilibrium right in cases where the reactant side has gases involved.

Key concepts

Le Chatelier's Principle

When a chemical system at equilibrium experiences a change in concentration, pressure, or temperature, it will adjust to minimize the stress. This response is guided by Le Chatelier's Principle.
It essentially means the system "works against" the change.
By doing so, it tries to restore equilibrium. Some ways to impose stress on a system and influence its equilibrium include:

• Changing the concentration of reactants or products
• Altering the pressure (for reactions involving gases)
• Modifying the temperature

In the context of our reaction equation, if we apply more of the given reactants, the equilibrium will shift to form more products, responding to the change in concentration.

Exothermic Reaction

In an exothermic reaction, heat is released as the reaction proceeds. This is seen as a product in the reaction equation.
For the formation of calcium carbonate from calcium oxide and carbon dioxide, the equation shows that 180 kJ of energy is produced.
Since heat is released, the system tries to produce more calcium carbonate when the temperature is decreased. Some key points about exothermic reactions include:

• They release heat into the surroundings
• The surroundings usually become warmer
• Lowering the temperature favors the forward reaction

With an understanding of these points, reducing the temperature causes the reaction to adjust and produce more product to create more heat.

Equilibrium Stress

Equilibrium stress involves any alteration in the system's conditions that affects equilibrium balance. Understanding these stresses is crucial to predicting how a reaction will respond and shift.
One such stress is pressure, particularly in gaseous reactions.
Adjusting pressure can influence the direction in which the reaction shifts based on the volume of gas particles. Key facts about stresses affecting equilibrium include:

• Increase in concentration pushes the reaction to use excess reactants
• Change in pressure might seem confusing when both sides have equal gas particles
• Temperature adjustments directly impact the heat equilibrium

By carefully applying these stresses, one can promote the production of desired products by leveraging the reaction's response mechanism.